need help getting oblvion to working properly

[stryke123]

hi, i recenty got elderscrolls 4 oblvion and when i play it it's really choppy even on the lowest setting, the choppyness is bearable but another thing that is happening is that the game freezes every 15 mins or so, but the funny thing is when it freezes the game dosnt stop i just lose all control and cant click anything and my guy will just keep walking until he hits a wall, but when this happens the game runs perfectly smooth, the enemies will attck flewently, people will be walking around, the faces of people when talkign will smooth out, no choppyness (even when my guy is walking and being attack)

so i was basically wondering if anyone knows anything about what might possible be happening here , i'm pretty sure that me pc can run this game better

specs:
AMD athlon 64 2800+
1.5 Gigs pc3200 ram
two 40 gig HDD
ati radeon 9800 128mb sapphire