1 - Virus, Trojans, and Other Malware 2 - Spyware and Adware. 3 - Fragmented hard drive 4 - Not Enough RAM 5 - Startup Programs & Background Applications 6 - Windows Registry Problems 7 - Windows Updates not current 8 - Full Hard Drive 9 - Graphics Hardware Underpowered 10 - Anti-Virus Software Too Restrictive
These are the top 10 reasons your Windows XP or Windows Vista computer may run slow