Although I can successfully install and use Vista Inspirat on my XP Pro SP2 system, but after a few days or so,the windows default applications like Notepad, paint ,default windows games vanish!Even System configuration utility was gone(msconfig)!Then I had to re-install Windows becuase repairing wasn't working.Why does this happen?Is there any way out to solve this problem?    

Very odd. I don't think this is caused by VI, as it doesn't even touch msconfig..
Are you sure you didn't do something else that might've caused this?

Very very odd. You're the second person to have things like notepad vanish... but I doubt it could be VI, since only one other person has had this problem (I'm not going there) and as Legace said it shouldn't even affect those kind of files and applications.

Either you've managed somehow to affect something that has caused this, or something has gone wrong with your system because of a virus perhaps, or even something as "harmless" as a windows update. Did you download anything, visit any sites that you don't on a regular basis, or install any other applications or updates perhaps?

Did you install Vista Inspirat 2, the new Bricopack?
Did you install it in safemode (press F8 during bootprocess)?

Usualy the bricopacks works fine  

I tried all of that when my desktop wouldn't load. All of my processes were running like normal but nothing was accessible... files, folders, progs....
So I has to do a sys repair.  

That happened to me only 2 weeks ago, everything was gone, even system restore. So i had to redo my computer. I think i know why it happened, i was trying to save Memory, so i deleted C;/WINDOWS/brickopacks. (I already uninstalled VI2 a few months ago) So i thought the file was useless. Did you happen to delete that file?

nilanko, joooce and Greenfire The things what you inform are not done by bricopacks but some of them ma be due to confliction of relavent system files (unless you've installde in 'safe mode' )

For your questions I can only think of computer viruses  
  Make sure that you've updated yor anti-virus programs (That won't always do the job though)

Greenfire If you've uninstalled a bricopack, deleting C>Windows>Bricopack folder won't do any harm