Win32 /heur - cd rom broken

[blackmagician]

hi, i am new to this forum. was googling my problem when i came to techspot.com . so i decided to post my problem here. i have had a virus problem since a month now. it would surface up sometimes and i would get rid of it before it finally showed its ugly head. it messed with the system files so as to kickstart data-execution-prevention and hence it would prevent things like dll-cache, generic host 32, userinit, etc startup things from executing. i got around with this by starting task manager ( which sometimes is prevented from running too. ) now, i installed AVG anti-virus, and it returned with loaaaaadss of Win32 /Heur and had the only option of "remove threat" . without realizing my mistake i deleted a few windows sys 32 files . now, the virus stays still at large along with a certain win32 /tanatos.m and has infected my executables to a certain extent. next thing i do is run rmtanat.exe from avg site . it cleans 100+ files (dont know the exact no. as it is still running ).. also, another thing is, my cd-rom is broken and i dont think i have a great chance of getting it replaced. so what do u guys think i should do ? ( at this moment i fear shutting down my computer too as last time around it kept on restarting after the windows files loaded ) . pplease reply reallllyyy soon

Anti-virus - AVG 8 updated
LAN + Internet Connected
Filesharing via Apex DC++ & Strong DC++
Windows XP Pro SP2
NO CD-ROM
External HDD of a friend for back-up

P.S. : Could the virus infecting an exe of my apex dc++ setup and cause it to generate a runtime 6002 float-point error ??

Edit:Also, the deleting of system files has caused my pc to run at a crippled speed ( i think it has to do with me deleting dll-cache ) .. so any tips on how to recover the system files ? ( cannot run sfc /scannow as my OS cannot find the command ) .