Hi
I'm planning to build dual boot system XP Pro 32bit+Vista Ultimate 64bit
For XP 2G Ram are enough but vista needs 4G especially with low prices now
I know the problem that XP will recognize 3-3.5G only due to 32bit limitations
But thats it ???
All hardware , software, and games will work properly ??
Microsoft insists that with 4g Ram , Vista 64 bit is a must !!!
Why it is a must??
Anbody knows if I'm going to face any problems ??

Best thanks for your input

Well I have had 4GB system and win XP for a couple of years now, without any memory related problems, so no worry in that aspect. Ofcource some part of that memory is wasted in XP use. The harder part is to get XP and Wista to work together...

Hannibal :

Thanks for your fast responce
If the only problem the waste of part of memory in XP I'm Ok with it
I'm planning to put each OS on a separate HDD
I think it is better than having each on separate partion of the same HDD

You will probably see only 2GB anyway under XP. Here's why.

On most motherboard, you need to enable a "memory remap" feature. That does affectivly take the memory between 2 and 4GB and remap the adress to over 4GB, all in hardware with no (very limited) performances loss.

The result is, with a system like mine with 6GB memory and dual boot XP (32-bit) and Vista (64-bit), you will see 2GB under XP (everything over 4GB adress range is invisible) and 6GB under Vista.

Even if XP need less memory then Vista, I prefer a lot Vista anyway. Any app can use at best 1.5GB memory with XP (total memory less background apps) while anyone under Vista can use either 2GB (32 bit apps) or the whole 6GB... well, say 4.7GB considering Vista use 1.3 at startup, less with apps launched.. Anyway, you should get the point.

Yes there are guite a lot differencess depending on your mother board. So it's good advice to look your mother board ventors homepages to see how you MB manages memory.
I have Asus board with ATI chipset, and I can use 3.2 MB of memory in XP (one aplication can still only use 2 MB, due the XP) But the USB-handling is not so good in my board... *sigh*