Doomknight, it sounds like you are able to install mods that are packaged in a certain way, but not others.
Here's my suggestion:
- Download mod to C:\downloads. You will need to create this directory.
- Start up OBMM
- Click on the create button at the bottom of the screen
- Click on the Add archive button in the middle of the dialog box
- Navigate to your C:\downloads directory and select the archive file (.zip, .7z or .rar)
- Click OK and wait. You should see some files listed in the box in the dialog when its done.
- If you are prompted to import OMOD conversion data, say Yes
- If no OMOD conversion data were provided, you will have to give the OMOD a name - enter that at the top of the dialog
- Click OK to create the OMOD. Don't worry about entering an author's name or description - just click OK when prompted.
- Now the OMOD should show up on the right-hand side of the OBMM window. Double-click on it to install the mod. The mod will be installed and automatically activated.
This should work for the majority of mods out there. OBMM usually does a pretty good job of sorting through the directory structure and putting things in the proper place. All of the mods in the Oblivion data directory will be displayed in the left-hand panel of OBMM. They will have a check mark next to them if they are activated. Just click on any mods that don't have a check mark to activate them.
NOTE: some mods come as OMOD's already. They will have an omod extension. Those just need to be copied to the omod directory under OBMM - I'm sorry, I'm still rebuilding my machine right now and I don't quite remember where that is normally. Have a look under your Oblvion directory or under your Oblivion\data directory for a directory called omod. Copy any omod's you might have to that directory and they will appear in the right-hand panel in OBMM for you automatically. All you need to do is double-click on them to install them from OBMM.
Lastly, you should download http://www.tesnexus.com/downloads/file.php?id=20516 and run that. You install BOSS into your Oblivion\data directory and double-click on boss.bat to run it. It will put all your mods in the correct load order, unless it doesn't know about them. If you get that far, post again and we'll help you sort them if necessary.