Windows 7 memory use - CS-4 question

Question

My XP machine is maxed out with 2 gig of chip memory (AMD dual core). Please, no laughing. It does run Photoshop CS 4 at an acceptable speed with 500 meg. PSD pictures.
Apparently, there is a way to set up the system drive to dual boot to Windows 7 or XP with a "virtual hard drive" set up. How much less memory does Windows 7 use as compared with XP Home?
With the early order half price for 7 Professional, it might be a way to give Photoshop some more memory (5%, 10%, 15%,?%) without having to get a new mother board and new memory chips at a far lower price.
I am using Photoshop in a non-work environment. My full time job, hasn't given me a pay raise, in the last 8 years, that matched the increase in health insurance cost, I am willing to accept less than optimal performance boost at an affordable price. And, as I'm paying off a month old Epson 3800, every little bit of savings helps.
I am aware that I might/will have to reinstall Photoshop under this set-up. That doesn't present any problem.
Thank you,
Bill

Answer 1

Zeno Bokor,
Your statement concerning Windows 7 reducing system memory use as chip memory decreases implies that the memory management is improved and that there would be more available for high memory use applications. It may not be much, but any extra would be an improvement. With a dual boot system, I would think that some services could posibly be turned off if only one program was to be run under that OS.
While Photoshop may not care about memory specifications, I suspect that, with faster chips, at least some actions it carries out do perform faster if there is sufficient memory to carry out the operation in memory, rather than in swap file. I am sure that the operating system does. I have done all the "boosting" I can do with three physical drives. One of which can be called Photoshop swap file dedicated. The machine certainly ran CS a lot faster than the one it replaced. CS-2, through 4 were installed only on this machine.
I know that more memory is very good. However, without a new mother board, I can not increase the memory in my system. That mother board must, for current financial reasons, be able to use the chips I already have as well as have additional open slots. Any Photoshop performance gain, from more chip memory, will have to be put off for an unknown time period.
This leaves me where I am now. That is: looking for a small gain in performane (available memory), with a different OS, that would carry over when I upgrade the hardware. The half price pre-release price is affordable. A new MB and additional chips, for about a year, is not.
Bill