Viruses can be easily eliminated by formatting the drive and reinstalling Windows, buying a new hard drive seems a bit exccesive...
You can take out your old hard drive, install the new one and install Windows no problem, although I wouldn't suggest moving any of your files to your new drive from your DVDs until you scan them all, as chances are some of them are infected.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w