How many times per year hard disk must be formatted..?
IMHO not unless you're really having problems with it....before a fresh load. Otherwise, just leave it be. Remember the adage "if it ain't broke, don't fix it". It applies here.
How many times must it be done? None, nothing requires you do that.
If your windows turns to crap multiple times a year its probably because of less than ideal user management of your system.
It's an extraordinay amout of wear and tear on you drives mechanics to carry out the entire process of formatting and reinstalling everything for no reason.
You don't even want to defrag more than once every month or so
I think it depends on the file format you are using. I have a XP with FAT 32 and find it could use defrag. every two weeks or so. But my PC with NFTS needs it even less often the once a month.
i want to change my hard disk root so i dont save to my c:\ but i save to my E:\ instead