SOLVED!

I bought the Steam version of Oblivion back in August, and have not been able to get it to start up properly. It goes through the intro credits fine, gets past that paragraph of legal information and then freezes. Or, if i hit esc to skip the intro bit, it goes to a loading screen, loads for a bit, then freezes. Back then ago, before I started asking for help on other forums, if i ctrl+alt+delete I got to an error message that said:

The feature you are trying to use is on a network resource that is unavailable.
Click OK to try again, or enter an alternate path to a folder containing the installation package "PureHD.msi" in the box below.

At the bottom of the window there is a box titled "Use source" and in the box it says:

c:\users\(my name)\appdata\local\corel\corel video

I checked for this directory, but it didn't exist. I used to have a demo of a program called Corel Video Studio Pro, which I uninstalled when the demo time limit ran out, so I assume that's what used to be there. I later went back and made sure it was completely uninstalled with a program called Advanced Uninstaller Pro 10.

I tried reinstalling Oblivion but it didn't help. Following the instructions of someone on another forum, I backed up my registry and then went through and deleted anything with "corel video" in it. (I know, really dangerous) There was ALOT of stuff. I got all of it except the ones in the:

Computer>HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Win dows>Current Version>Installer>UserData>S-1-5-18>Components

directory. There are hundreds of them in there, in folders with names of random numbers and letters. They are all "REG_SZ" type entries. It would take me a week to delete them all. But, Oblivion still wasn't working.

After deleting what I could of the registry, I found that the error message had changed. It now reads:

The feature you are trying to use in on a CD-ROM or other removable disk that is not available.
Insert the "PureHD" disk and click OK

There is a box at the bottom titled "use source:" the entry in the box just says "1" and there are three buttons, OK, Cancel, and Browse.

I tried re-installing the Corel Video Studio Pro Trial, but it wouldn't let me complete the installation. I believe this is because I already used up all my trial time.

I downloaded TweakNow PowerPack 2010, on the advice of someone on another forum, to clean my registry, and it seemed to find things that needed cleaning, but that didn't do the trick. Oblivion still wasn't working.

I saw that it had an uninstall programs feature, so I decided to check and make sure that all of Corel Video Studio Pro was gone. I found three programs that all shouldn't have been there, one named PureHD, one named VSClasic and one named VSPro. I uninstalled PureHD, then when I went to uninstall the other two it gave me an error message saying "This action is only valid for products that are currently installed." but they went off the list, so I figured that was fine.

I restarted, absolutely sure that Oblivion would be working when I started back up. But this was not the case. I went in and checked TweakNow again, and those same three programs were back on the list. I uninstalled them again, and refreshed the list, and they were back again.

"Try booting windows in Safe Mode and then running the registry cleaner you have..maybe the background program keeping those up will not run in safe mode"
That didn't work

"It looks like the Video Studio trial installed it's own video codecs and set them as standard. Try reinstalling Windows Media Player. That should sort the codecs out."
Also didn't work. I also reinstalled VLC media player, which I use more often, but that didn't work either.

At this point I gave up and waited until yesterday before picking up the project again. I'm not running any mods. I bought the deluxe edition from Steam, so I have all the official DLC that they offer. I tried disabling the dlc with oblivion mod manager, after seeing something about that on these forums, and made sure that oblivon.esm was loading first. I've reinstalled and validated my game cache several times. I've tried running it without the steam overlay. I'm sure my system is powerful enough to run oblivion. I checked the System Requirements Lab's "Can You Run It?" thing just to be sure, and I passed everything for the recommended settings except the operating system (I use Windows 7). I think that's about all the info I have. If there is anything else you need to know in order to help me, just ask. Thanks in advance.

EDIT:
Some more info. I tried CCleaner after it was recommended by a user of another forum, and scanned registry for errors. Found some, told it to fix them all. Restarted, ran Oblivion, no change. Was browsing over the rest of CCleaner's features, found the tool that removes start up files. There was one in there that said:

HKLM:Run Standby "c:\Program Files (x86)\Common Files\Corel\Standby\Standby.exe" -START

It was disabled, so I enabled it and restarted. Nothing different, nothing new about corel in the registry. So I deleted it, restarted again, and nothing. Also checked the Uninstall tool for those programs PureHD VSClassic and VSPro, but they weren't on the list.

Also tried deleting the Oblivion.ini in the My Games/Oblivion folder, which also did not work.

I read over your entire post and then did some searching via Google. It would seem your problems are indeed associated to PureHD.msi. Many other users apparently have problems uninstalling this program. Especially if it's an illegal version. I found the following quote somewhere that involves a registry entry you did not mention above.



I found http://www.geekstogo.com/forum/topic/269443-cant-uninstall-corel-purehd-fully/ short forum topic with a few apparent solutions.

Upon further searching I found http://www.instant-registry-fixes.org/how-to-repair-windows-installer-error-1706/ will likely help also.

I don't think this is anyway an Oblivion or STEAM issue, but it's related to codecs installed by PureHD. Also apparently removing that program is a pain for some, since it leaves remnants behind. The above links should help out. If not I can only suggest you continue to search for ways to safely and completely remove the unwanted software. If it's malicious (possible from a torrent site) and you cannot remove it then you may be forced to format your drive.

Good luck.

I looked at those posts, and then went into my registry again looking for that key, and I couldn't find it at that location. So I just searched USIShellExt and found a few entries with it in there. One that looked the most promising was at HKEY_CLASSES_ROOT\Wow6432node\CLSID\{DBD8E168-244D-448C-9922-25508950D1DC}, but I didn't want to go deleting things I wasn't sure about. Is this likely what is causing my problem?

Also read a bit further down the first link to find someone talking about installing Windows Essentials Media Codec Pack 3.0 to get all the codecs to straighten out. So I went ahead and tried it but it didn't help.

The second link was a bit confusing. It talks a lot about installing things, which I'm not trying to do. Maybe I'm just reading it wrong, but I don't thing it has much to do with my problem. I've come across the error 1706 thing before in my searching, but always in reference to Microsoft Office, which I don't have on my computer, so I didn't think much of it. I tried the registry cleaner that the site recommended anyway, and it seemed to do (I think) pretty much the same thing as CCleaner, but it wanted my to pay for it before it would actually fix any of my problems. I don't really see a point in paying for a program that does the same thing as a free program I already have.

As for whether my Corel demo was malicious or not, I don't think it was. I got it from a teacher at my high school last year, so I can't be absolutely sure where it came from, but it's just a demo, so I can't imagine why it would have come from anywhere but Corel's website.

So I was searching through the registry, I think it was for Ulead this time, after reading that first link again I thought it was worth a shot, and I came across a directory called .VSP/OpenWithList and in there were some keys, one named "a" with a value of VStudio.exe and one named "b" with a value of Oblivion.exe. So I changed the value of a to Oblivion.exe, restarted, and it worked!
So, thank you so much for your help, couldn't have done it without you.