I had this problem when I first started but when I try to open a file with OMM it 9/10 times say the file type is unsupported. I use to know a way around this but it has been a while and I have forgotten.

More details would be good. Guess you mean OBMM? It supports omod-files, but you can also use it to create omod's from archives (it supports the major ones at least) or from folders.

Oblivion Mod Manager. I tried to add this mod but is says unsupported file type: http://www.tesnexus.com/downloads/file.php?id=25101

What happens when selecting the mod through the normal Oblivion launcher ?

There is no option and now the damn game won't load past the intro bethesda screen. :/ I clicked add archive then I was able to add the file. Tried to load up the game and pretty much an instant crash every time. I deleted it but nothing has changed.

But that isn't a mod, it's just a spreadsheet with links to mods. :unsure:

Artorius.

That isn't a mod - that's a list of mods in xls-format. Open with Excel or equivalent.

Oh. I'm not very good with mods and the videos I have watched have not helped. Anyways I had this file called Knights unofficial patch.esp and Knights.esp and they use to work fine but I have to turn them off now.

Edit: I tried to open it in a spread sheet program, but it keep opening it up in a word type document

I'd start out very slow if I were you, otherwise you will only mess things up. You will need to manage the load order for one thing - in the case above the Knights - Unofficial Patch.esp needs to load after the Knights.esp. Use BOSS for managing the load order - you'll find the thread on the first page here. Also, can you post your current load order? Via OBMM: Import/Export > View load order > Copy all (CTRL+A, CTRL+C) > Paste into post (CTRL+V).

Oblivion.esm
DLCOrrery - Unofficial Patch.esp
DLCFrostcrag - Unofficial Patch.esp
DLCThievesDen - Unofficial Patch.esp
DLCMehrunesRazor - Unofficial Patch.esp
DLCVileLair - Unofficial Patch.esp
DLCBattlehornCastle - Unofficial Patch.esp
IWR-Windows.esp
IWR-Lights.esp
IWR-Shutters.esp
Alternate Start Revamped.esp
AliveWaters - Slaughterfish Addon.esp
AliveWaters.esp
BWisteria.esp
Zooloo75's Weapon's.esp
Ians long sword.esp
xulRiverEthe.esp
xulSkingradOutskirts.esp
xulSnowdale.esp
xulStendarrValley.esp
xulTheHeath.esp
xulCliffsOfAnvil.esp
xulRollingHills_EV.esp
xulPatch_AY_AC.esp
UOP Vampire Aging & Face Fix.esp
Oblivion Citadel Door Fix.esp
DLCThievesDen - Unofficial Patch - SSSB.esp
DLCSpellTomes - Unofficial Patch.esp
Unofficial Oblivion Patch.esp
Unofficial Shivering Isles Patch.esp
DLCHorseArmor - Unofficial Patch.esp
SwordOfTheEye.esp
Arthur_Natural_Weather_HDR_by_Max_Tael.esp
KT_CustomRaceFix.esp
ZelsHairfixRenshairV1_5.esp
DLCHorseArmor.esp
DLCThievesDen.esp
DLCFrostcrag.esp
DLCSpellTomes.esp
DLCBattlehornCastle.esp
DLCMehrunesRazor.esp
DLCOrrery.esp
DLCVileLair.esp
DLCShiveringIsles.esp
xulAncientRedwoods.esp
xulAncientYews.esp
xulArriusCreek.esp
xulAspenWood.esp
xulBlackwoodForest.esp
xulBravilBarrowfields.esp
xulBrenaRiverRavine.esp
xulCheydinhalFalls.esp
xulChorrolHinterland.esp
xulCloudtopMountains.esp
xulColovianHighlands_EV.esp
xuldarkforest.esp
XulEntiusGorge.esp
xulFallenleafEverglade.esp
xulImperialIsle.esp
xulBeachesOfCyrodiilLostCoast.esp
xulLushWoodlands.esp
xulPantherRiver.esp

Yes, first you need to run BOSS to sort your load order. I'd also start out with much less mods - start with getting the UOP and the DLC's plus patches working.

All of that works just when I turn on the knights files the game crashes as soon as it starts. I was just playing a sec ago. Also what is BOSS I have it in my programs but I get the unsupported file type problem.

http://www.gamesas.com/index.php?/topic/1179974-relz-boss-better-oblivion-sorting-software/. You need http://www.rarlab.com/download.htm or http://www.7-zip.org/ to be able to open archives (i.e. downloaded files that end with .7z, .rar, .zip etc.) so that might be one of your issues. Then, check the readme for BOSS on how it works.

So I should download the BOSS 1-65 Archive? Do I need to DL the BOSS 1-65 Installer? I lucky I was able to get the other mods to work, now it seems like my luck has run out.

One or the other. The first is for a manual install of it - the other comes with an exe-installer I'd guess so just to double-click and follow instructions.

Thanks! At first I thought it did nothing but then I realized that I needed to activate the Knight files and now every mod is active and it all works.

You're welcome! Yes, the most common reason to get CTD's on startup is because a master is missing. In this case Knights.esp is the master of Knights - Unofficial Patch.esp (i.e. the latter requires the former) - so if not having Knights.esp checked while having Knights - Unofficial Patch.esp checked it will cause a CTD on start up.

One last question that is not a big deal. After I exit the game it crashes. Like when I save an turn the game off to go back to my desktop. It really is not a problem, but I'd like to know why this happens.

It's a very common issue when using lots of mods. http://www.tesnexus.com/downloads/file.php?id=22410 will ensure that the game closes down quickly instead. Requires http://obse.silverlock.org/.