Windows Vista forum: blank screen at startup

Im 90% sure this is caused directly or indirectly by a virus I accidentally installed through a program I wasnt suppose to install. First things first here are my laptop specs:

Asus A8JP
C2D 2.0gHz
2GB RAM
Windows Vista Home Premium
ATI x1700 (catalyst 7.9 drivers)

So I ran the virus/Trojan program (not knowing it was, even though AVG warned me not to runfoolish move on my part) and a windows error window showed up saying something about needing to protect my computer and explorer.exe shut down along with other programs. So my computer restarts, I see the ASUS screen, then the windows is starting screen. Then when it should get to the windows login screen, the screen is black and stays black after 5-10 minutes. If I vigorously move my mouse cursor while its starting up, the same black screen persists but I can now see the white mouse cursor and can move it around the black screen. Also when I press alt-tab I see 2 programs running and can alt-tab btwn the 2. One does not have a name (Im presuming its the virus/Trojan program thats preventing windows from starting up) and the other is named windows logon so Im guessing windows log-on is definitely running, but that unnamed program is preventing me from seeing the log-on screen or accessing the log on screen. So here are thigns Ive tried (w/o any peripherals plugged into my laptop)

1. Safe mode starts up until the screen where the drivers/files are being loaded, and the please wait screen, but right afterwards when its suppose to go into the desktop in safe mode, the machine restarts automatically in non-safe mode, brining back to the black screen I decribed before.
2. I inserted the windows recovery cd and cant restore my computer to a previous restore point because I turned that feature off. I tried to automatic repair service but after the repair I still get the blank screen.
3. I can use the command prompt via the recovery CD and have tried running chkdsk which resulted in no errors. I also tried running sfc /scannow but I get the message Windows File Protection could not be initiate a scan of protected system files

Im pretty confident the virus program has maybe indirectly or directly altered system files or display drivers so that I cant access the log-in screen, or prevents me from booting into safe mode.

Is there any way I can boot from a USB disk drive that has a anti-virus scanning program I can run to rid the virus? Right now I can not even access safe mode nor the desktop, but can access my BIOS screen and the vista recovery CD.

I really hope to fix this blank screen problem w/o reformatting my hard drive as I have not backed up my personal files and do not wish to loose them. Thanks.