Jim Hawkins wrote
Clive George wrote
Jim Hawkins wrote

What do you gain by upgrading from
XP Pro to Win 7 Pro ?

Support/patches.
64 bit if you're sensible and hence ability to use more than 3G memory.
Task manager is better.
It's more stable IME.

And what do you lose ?

Money if the upgrade costs?
UAC can be a bit of a pain if you set it up wrong.

Is it possible to upgrade a 32bit machine (whatever the OS)
to its 64 bit equivalent - or do you have to buy new ?

Depends on what you bought. Some do come with both versions.