Vista Tutorial - H/W probs

hey all, i was running Windows Vista RC1, but i needed to get a driver for my
graphics card cas The Sims 2 wasn't displaying itself correctly (i think it
forced itself in to DX7 support :P) i got the new graphics card driver and
installed it, but when i rebooted, i got the following error "I/O disk error"
but that was cas i had a flash drive plugged in, so i rebooted again, without
the flashdrive and it booted up again, but the sims 2 didn't run properly
again, so i was going to ajust the hardware acceleration, but when going to
display setup, something "popped" inside my tower, but the OS didn't freeze,
so i unplugged it, and opened the case, nothing looked burnt, though there
was a small burning smell, but i noticed a screw on the bottom of the case
rolling round, would the screw have dropped on the mobo and zapped it? it is
kinda confusing. here are my PC specs

Case: eMachines 420
Mobo: ASRock P4VM800
RAM: 512mb (2x256mb, PC2700 and PC3200)
Graphics: VIA/S3G UniChrome Pro IGP
CPU: 2.6GHz Intel Celeron 128k northwood
HDD: Maxtor 5400RPM 80GB HDD
Optical Drives: x16 DVD-ROM & x48 CD-RW
PSU: Q-TEC 500W PSU
Floppy: 1 1.44mb