I am afraid this does happen in Windows Vista!
Suddenly my Vista computer had a very bad performance and everything started to work
very slowly, especially windows mail.
The Task manager showed that CPU was constantly at 50% - 80% even if I was
not doing anything and let the computer untouched for a few hours.
Most of the CPU time was taken by explorer.exe.
After trying many things and struggeling with this issue for many many hours,
I slowly got some idea.
Appearently something under water goes wrong with your user profile and the search
index settings of the files in your USER folder. Vista tries to index stuff in this folder
and gets completely crazy. It keeps on trying and trying and eating up most of
your CPU time (explorer.exe).
The only lasting working solution, I found was to make a completely new User Account.
After making the new User Account, you can only copy a limited number of stuff
from your original User Account. Some stuff when copied to your new User Account
will again make your new User Account go crazy.
Also, I turned off the search indexing for the new User Account, including all subfolders.
Here is what I did:
* Backup your original User Account, Mails and any other critical files.
* Make a new user and make an extra help account (for example called: admin with Administrator rights).
* Make sure that the search indexing for the new User folder is TURNED OFF
(via properties of the folder -> Advanced)
* Manually and carefully only copy back stuff you really need.
* Use Command line with Administrator rights to copy User stuff step by step.
The moment you see the CPU getting crazy again, delete the last User stuffs you just copied.
To restore your e-mails:
1 - copy the e-mail folder to another partition in folder mail2 (for example: f:/mail2).
2 - in the new user login, set the archive folder of Windows mail to f:/mail.
3 - delete f:/mail and rename f:/mail2 to f:/mail (BE CAREFULL! make sure you have a backup).
It's quite a headacke, but it will bring down your CPU to 2% - 10% when you are idle.