Re: dual booting system
It can be done; there are plenty of tutorials on the internet telling you how to do it. The key is getting the bootloader(s) to work correctly. Windows is a bit trickier to install second, but usually you can install a newer version next to an older one and the newer NTLDR will point to both.
The OS's are pretty much separate, the machine won't care whether it is a 32-bit OS or a 64-bit one, as long as the code is written for that processor.
I am currently dual-booting Win 7 and Ubuntu 10.04 (both 64-bit), though I used to multi-boot Win XP Pro (32-bit), Ubuntu 08.04 (32-bit), and Ubuntu 09.10 (64-bit).
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