My pc's been running really slow the last couple of days & when i say slow i mean SSSSS LLLLLLLLLLLLLLL OOOOOOOOOO WWWWWWWWWW

Every single thing is taking ages to load, any forum i visit, any reply i type etc etc

I've run spybot & cc cleaner but it's not any better

Any ideas people?

Im on Virgin Media broadband btw.