As above, and if you decide to remove files or compress them, give the hard disk a defragmentation once you're done. This will sort the files on your hard drive so that they are not fragmented and don't have gaps inbetween. This is what causes the execution of programs to be slow. You'll find the program under: Start>Programs>Accessories>System tools>Defragmentator (or something similar, translating from polish) This will take a long time, especially if you haven't done it in the past. Leave the computer on over night. edit: These are some programs Tomturd mentioned: Spybot program - A good free anti-spybot program AVP - Anti virus software, I think it's still free