This trojan/virus got onto my computer and has i believe taken up 80GB of 320GB drive. i got the virus removed but how can I reclaim my drive space short of reformatting? The space shows up as unmoveable when I run Smart Defrag. WinDirStat says I only have 137GB on the drive.

I would appreciate any help

The easiest way is to reformat the unused space as a new drive partition.

The other way (not recommended) is to use something like Partition Magic to append the unused space to an existing partition. This is very time consuming and also runs the risk that the Master File Table will become irreversibly corrupted in the process.