Trig (or may I call you GSV)?
Let's take these PCs one at a time - all of which, of course, must be running XP.
PC1 - Q6600 CPU and 4GB of RAM
I have to assume that this is running XP 64-bit.
If it's not, then from the little I know about this matter, I reckon you've got in there more RAM than is needed - in fact sufficient unneeded RAM to actually slow down the performance!
But irrespective of that, if you had 2GB, (like PC2 with an E6420 processor), I'd still imagine that eBoost wouldn't help much until you get to a situation where XP is looking to swap stuff out to hard disk - and, on a well-setup PC, that can require a whole lot of apps to be loaded all at one time.
Right now (on my 2GB E6660 PC) - and, admittedly I've got considerably fewer apps loaded than I often do have - I'm using just (did I say, 'just'?) 1.05GB of RAM.
That's while running Firefox (one window, 11 tabs); Outlook 2003; Thunderbird; and MS Word 2003 (one small, two-page doc open). I'm also printing 100 copies of that doc at the same time.
Running in the background - among other things - are Kaspersky Internet Security Suite 7.0; Google Desktop; Skype; HotSwop!; and SpeedFan 4.32.
So here, even with all that going on, I can't see how eBoost could help me.
Not sure what your free memory is on the first two PCs while working 'normally' (whatever that might mean) but unless you are running some massive memory/resource hogs (Norton Anti-Virus and McAfee come to mind), I can't see how eBoost could possibly help you.
However, I'd suspect that quite the opposite is true of PC3 - your laptop (P4M 2GHz CPU; 512MB RAM).
But, I have to say that I do find very intriguing your idea of using a memory stick as the place for your swapfile/page file, rather than hard disk.
Indeed, I think that, in fact, you might be quite right in suggesting that this is an especially effective way of using a USB stick drive for speeding up a PC that didn't have much RAM.
Mind you, if you had two in there - one for the swap file and one for eBoost - you might find there was then a very profound overall improvement!
So, what I'm going to do is see what happens when I use two USB stick drives on my likkle Dell - a 1GB for the swap file and a 2GB for eBoost.