Vista changes desktop if I change processor/memory speed in BIOS

Hello!
I have the following problem. I have a desktop with lots of icons/folders on
it. However when I change processor speed in BIOS and login back to the only
account I have on my computer, Vista shows "preparing desktop" and then gives
me the default desktop with "what's new in vista" window, as if I just have
installed it. Also some programs are not running that I run by default in my
account. If I change processor speed back (through BIOS and windos restart),
the desktop recovers.
How can I change processor speed and still be able to see my old desktop and
configutatin? I did not have this problem in the past (about 1 year ago) and
was able to change processor speed and still see my desktop.
I have Vista 32 home professional. I do not know if it is important, but my
account name and folder name under "Users" folders are different, because I
have changed my account name in the past.
Thanks.