did you clean up the temporary files? sometimes they pile up and slows down the system.
is your hdd defragmented?
how do you allocate your system's virtual memory? you can see it from "Control Panel\All Control Panel Items\System" > "advanced system settings" > "advanced" tab > "performance" > performance "settings" > "advanced" then virtual memory. is it dynamically managed("system managed file" selected) or both upper and lower limits are same? edit: is the pagefile in the o.s. drive (usually c

or in a different partition/drive?
how old is your anti virus software?