I have a notion that your techie might have been talking about the upper limit on the useable RAM in a 32 bit system. I ran into this issue when I bought my wife a PC (Pavilion as it happened) with 4Gb of RAM on board. My techie explained that, due to the architecture of the system, whilst running Vista 32 bit, it could only actually use around 3 of the available 4Gb. If I wanted to avail of all 4Gb (or more), then I would have to upgrade to a 64 bit OS. At least I think that's what was explained to me... I'm not deeply techie but Im sure someone on the forum will soon put us straight if I've misunderstood that stuff.
marty