Data corruption in all my downloaded .zip files

this has been going on for about 6 months now. I had started using the
site Direct2drive.com back in 2006 and had great success with their
service. I had downloaded a few games from them, some fairly large
like Neverwinter Nights 2. but around March somewhere I began having
problems. I downloaded Oblivion from them and ended up having a
massive amount of corrupted data in the .zip i downloaded from them.
at the time i was using winrar for my .zips so i downloaded a winzip
trial but experienced the same problem all around. It really shouldnt
have mattered either way since the downloader for D2D.com has its
own .zip unpacker anyway. But ever since then I have been having
problems with data corruption in any zip files or bit torrents I
download. For some reason movies seem to be fine, but video games are
always corrupted in some manner. anyone know of what could be causing
this data corruption or what I can do to try and pinpoint what the
problem is? I did a scandisk and checked my hardrive for any damage
but it came back as being fine, and I've defragged it to complete
cleanliness.