If You Buy A Windows Vista, Will Upgrading It To Windows 7 Lower Window 7′s Performance?
I’m thinking of buying a Windows Vista desktop computer with a free upgrade to Windows 7 when it comes out. I hear many good things about 7, but I’m wondering… If I upgrade to 7 from Vista, will 7′s performance be worse, than it would be if you bought a computer with 7 already installed?

No, it will make absolutely no difference at all, and in fact, Windows 7 has been designed to run faster than Vista so you should notice an increase in speed when you switch from Vista to 7
No. Of course not. Installing 7 on a computer would essentially remove any evidence that Vista had ever even been there.
no.but it depends on the size of your RAM