Two things to check first.
1. startup programs, especially those which "call home".
2. Uninvited guests or visitors.
Ive been using Incredimail for awhile, and think its a pretty good program. I also routinely defrag and run other utility programs to keep my HD in good working order. However, whenever I run a program to clean up the Registry, Incredimail stops functioning, so Ive stopped using such programs. Lately my computer has started taking longer and longer to boot, and I think it may have to do with a fragmented, cluttered Registry. Any suggestions?