If you use your computer to produce money to live on then I'd go for a 32bit version rather than the 64bit, just for simplicity. Much more important to get good solid reliable hardware and concentrate on known bottlenecks, which may not be the memory?

I can tell you that the current (2009) versions of Norton IS and AV work under VISTA 64  but not all aspects of ancilliary functions do including I believe Right Mouse Click context menus.

On driver signing, someone else perhaps can comment on this but the other day when I was looking for something else (why a paper dictionary or encyclopedia is so educational) I came across a statement on a Microsoft page that seemed to indicate that you could tell VISTA 64 to ignore Driver Signing.

Sorry but I did not bookmark it since I'm not using 64bit.

>>the 64 should be faster

Nope.  64 bit instructins run SLOWER than their 32-bit counterparts.  Also, just because Ram is "available" does not translate to it being USED...

64 bit DRIVERS are still an issue.  If you have plder stuff (printers, scanners, etc.) make sure there are 64-bit drivers available BEFORE you make the move...

>> I think "Mandatory driver signing" could be a problem.

That's what I was refering to with DRIVERS - 64 REQUIRES signed drivers...

>>My main reason for considering vista 64 is speed

Wrong reason for considering 64, IMHO.  Go 64 if you have apps that REQUIRE more than 2G application space (photo editing, video rendering, that kind of thing)...

If you are looking for "pure speed", go with Intel's just released I7 - the Quad-core part that sells in the $300 range here in the states runs FASTER than the Core-2 Quad-Core chip that sells for $1500.  It also uses triple-chanel DDR3 Memory that has far more bandwidth than what Core-2 Duo can provide...

You get "speed" from the hardware, not the bitsize of the OS unsless you are running a specific application that is memory constrained in the 32 bit realm...

I don't know what generates the message you posted, but as far as I know a signed .CAT file is required in 64 bit land...

I don't run Vista 64 any longer - I looked at it in the Beta stage but never went past that...

Were you running this locally or over a Lan?

>>What do you think the difference in speed would be having this processor but with XP.

Blazingly FAST (compared to your current configuration).  The i7 is the fastest thing Intel makes that is available for the Desktop...

>>The vistas' I have on my laptops aren't that fast,

When doing what operations?  How much Ram on the Laptop?  If anything less than 2G, that often will be a reason for performance issues...

>>the processor isn't that fast

Are you doing CPU intensive things?  Most any CPU purchased today is faster than the Pentium 4 you have in the Desktop...

Also, believe it or not, SOME new Laptops shipped with a 4200 RPM HD.  That will be "slower" that the more common 5400 RPM drive.  I have not seen a major performance difference with 7200 RPM Sata drives, FWIW...