Vista Ultimate + TES4 Oblivion = 5mins gameplay

As the title suggests, that is exactly how long Oblivion will run on
Vista Ultimate, and it's the GOTY edition of TES4.
Had the game for a full year now, didn't have this issue before, but
now the game will only let me play for a maximum of 5mins.
I ran it as Administrator: same thing.
Tried nearly every Compatibility setting: same.
Uninstalled & Reinstalled: Same.
Turned off unnecessary processes: Same.
That file that caused oblivion to crash isn't on my pc (mped2dmx
something file).
Updated everything as best I could, even did manual updates from the
microsoft site: same.
And before you ask, The game is bought an paid for from Fred Meyer, no
cracks or whatever (saw a post where an admin or member asked that
question, and no that post is NOT related to my issue).
I called tech support for TES4, they told me that it isn't designed for
vista, which I knew for a fact that it does work with it. So please, if
ANYONE knows how to fix this really annoying issue (And yeah the game is
installed with updates), please let me know.

And just in case anyone asks:
Biostar MotherBoard PCI Express
3.20 ghz P4 Processor
3 gbs of Ram (Crucial Balistics)
160 gb Hard Drive (dunno the brand)
Dell Optical Mouse & Dell Keyboard (if that matters)
Built in Sound Device (so no sound card needed)
Nvidia 8600 GT (Funny that it ran on my previous 5900 FX, but not this
one)
Windows Vista Ultimate 32bit (With The Service Packs)

The game ran ok with my previous hardware, but now oddly it doesnt want
to run at all. The weird this is, it doesn't crash or freeze or kick
back to desktop, it just disables my mouse and keyboard after 5 mins of
playing. The game still goes on, my character still slowly moving
(showing that hes breathing) and with a rat walking back and forth, I
haven't made it out of the first Dungeon of the game yet!

Seriously, help me here. And if you guys need a DXdiag, you'll need to
tell me how to create one to send to you guys, haven't figured that
thing out yet.
And for further overkill, did Scan Disk, Defrag, MemTest, and virus
scanning, still the same issue. No BSOD, if you are curious. If theres
anything that you guys can tell me that'll get my game working, PLEASE
help me out. Thanks in advance.
Pm me if I take too long to respond, I always check my emails, but I'm
joined with so many sites that I usually lose track, thats another just
in case. Thanks alot to everyone that helps out!

Gyrannon


--
Gyrannon