26Gb as Inthewayboy said, seems quite a load! I wud also suggest CCleaner- its a great free utility, besides the spyware scans which everyone suggested, i would also suggest that after the cleanup you run chkdsk and then the defragmenter, in fact since you do add/edit/delete lots of files, it would be gud to run a disk cleanup and defrag so that ur drive doesnt get cluttered. Setting an automatic defragger wouldnt be a bad idea as it defrags the MFT and paging file and will run daily and defrag whenver needed.