try cleaning the temp files and internet cashe.
although *that* much of slowness.... it's strange.
besides... if it's new...
I'd just say reinstall windoze. after five tries yo uget a working one. maybe

...did you instal any big heavy programs lately? (like antivirus from a famous, big software company norton (symantec) or McAfee ? those slowed my PC down terribly and thus are gone now)