That's your assumption only, that it is a virus. I doubt it.
First thing to do: toggle System Restore from on to off and back again to on. Makes a LOT of difference.
Then download a free program called treesize and see in what folders and subfolders your disc space goes.
You might like to use Windows Explorer to search for recently created or changed files also.
I have a Sony Vaio with Windows XP, the Vaio splits it's HD into two separate ones, C drive and D drive. C comes with 13.9 GB and D comes with 55.5 GB. I have recently started receiving alerts saying my C drive doesn't have enough space, so I checked and all of a sudden my C drive went from multiple gigs of free space to a few hundred MB. Over the past week my C drive has been getting lower. I will uninstall a program or delete files and it will only get smaller (yes I emptied the trash can). My drive went from 111MB to 650MB to 812MB in less than one minute. I can sit there and watch it change. This is NOT an issue of too many programs or files. Yes I delete my temp files and cookies and all that. This is far too random to be just a disk problem.
Has any one else had these symptoms and found it on virus scan? Because my scan doesn't find anything.