Windows xp reverting

Hello,

My pc ..a Dell one..has xp home edition version, All of a sudden last week it reverted back to a initial state where, after I logged on it started as if I was using the computer for the first time. All my files and documents were still saved and none of my files got deleted.

But all my settings got deleted like my desktop themes, screensaver, fonts size and all those. When i opened IE it showed me a welcome package saying "New to IE 7"All my history was deleted and websites were deleted from the dropdown. Even my homepage could not be found...Also my start meny was changed looking ancient.
So i system restored to previous days and it all came back.

But this keeps happening everytime i boot up my pc. I then restart (not restore) it again and all my settings come back.

I have been using this computer for over 2 years and all has been fine.

Could someone please help me with this as it is very annoying to restart everytime.
Also i am not the only user on the desktop. But nothing major has been done by either of us.
Thanks

Eddie