How many times can W-8 be installed ?

Hi everyone,

As I have a genuine MICROSOFT WINDOWS 8 Installing Disc with Product Key, I'm wondering how many times the operating systen can be installed on the same Computer ?.

I've been told it's unecessary to uninstall WINDOWS 8 and if I wanted to go back to WINDOWS XP,
this can be installed over the existing OS. Is this correct ?.

How can I find out wheather 32 or 64 Bytes have been installed ?. What is meant by 32 Bytes ?.

Hoping someone can advise me.

Cheers,

TONY CROSSLEY.