32bit XP switching to 64bit XP

[14k]

Can I use my 32bit Windows XP Pro cd key on a 64bit Windows XP? Basically I need to reinstall my OS and thought I would move onto 64bit because:
64 bit is more embedded now
I've bought another 2GB of RAM totalling 4GB
I have an X2 4200+ 64 CPU.

Do I have to go out and buy another copy of windows!?
If not, can a legit copy of 64bit Win XP be downloaded and my legit 32bit Win XP cd key be applied during the installation process?

Many Thanks

 

[Billb2]

No, yes, no.

 

[14k]

Thanks,

I would go straight to Windows 7 then, but since it's not out I may have to get the 64bit version of Vista now and get the free upgrade come October.... Annoying, but oh well.