Thanks for the replies and that link Mucks.
I'm having to delay my Vista installation as I've run into a problem with my second machine.
I swapped the Corsair memory from the AMD machine with the OCZ memory that was in the Intel machine (2 x 1Gb in each case).
Together with the new Corsair memory this then gives me 4 x 1Gb identical Corsair memory sticks.
When I put the OCZ RAM in the AMD machine, it threw up a lot of errors on boot. This situation deteriorated, through forced low graphics, countless errors mostly based around running applications, until it wouldn't boot at all.
I first tried a repair on Win XP which didn't help and then formatted drive C and went for a fresh installation, assuming that somehow Win XP had become corrupted. During the installation Win XP told me my hard disk had damaged sectors so I suspected a faulty hard disk.
I downloaded latest version of The Ultimate Boot Disk, made a CD from the ISO and ran a few tests.
Western Digital disk manager showed the disk was fine, both on quick and extended tests. I then wrote a string of 0's to it, effectively wiping the disk, using the WD tool.
Then I ran Memtest. Straight away, almost, I got 23 errors.
I then put 2Gb of the Corsair memory in, ran Memtest for an hour - no errors at all.
Next I tried one stick of OCZ memory at a time and with the first one fitted the machine refused to boot. A-ha.
At this moment Memtest has been running on the second stick of OCZ memory for around 30 minutes and has so far shown three errors.
So it looks like somehow I have two faulty 1Gb sticks of OCZ memory.
I'm wondering how could this happen just transferring them between two machines? The only logical explanation and one which, if true, I find really difficult to believe, is static. I must confess I did not ground myself before handling the memory, although all the Corsair stuff is still good.
I purchased the OCZ memory from E-Buyer in March 2007 so I'm just about to contact them with a view to an RMA.
This means, assuming I get the AMD machine up and running ok with a fresh install of XP, my Vista installation will not only be delayed but go ahead with just 2Gb of memory.
Strange how things twist and turn eh?