Wow! I thought my 8 minute boot time was bad. In my case, Windows decided to change my hard drive setting from DMA to PIO. So, whenever Windows access the hard drive, the computer would slow down.
If you want to be daring, here is a small guide how to check/change settings:
Troubleshooting: Enabling/Checking DMA in Windows Vista, XP, 2000, Me, 9x - Club MyCE
I am not a Windows expert, and I no longer use Windows, so I wouldn't want you to lose everything on your HDD. But, I suppose there is no harm in checking to see if your HDD is using DMA.
