I've spent the last 3 years with 1 gig of ram. 4 is the most it will take. I was looking at AVG's analyser and it showed that doing very little with my computer was using 750 megs of ram so I thought I would try adding a bit more. Processor use was something like 2% at the time. Things get slow if I add a drop shadow on a large drawing in Corel for example.
I've been looking at new computers and it appears that it's pretty hard to find one with a parallel port. I need at least one but I guess they still have pci slots? I also would like to stick with XP because of drivers. I didn't look but I doubt my plotter has windows 7 drivers available. Maybe I need to talk with a computer guy about what I should get.
You don't thing upping the ram will do anything for me?
On Windows 7 you can run things in XP compatibility mode as well. That may be the way around the driver issues, however, unless your devices are out-dated, there should be updated drivers specifically for Windows 7.
As to whether or not more RAM will help you, it depends on the limitations of your processor and even your graphics card. You might be able to physically fit 12 GBs of RAM, but your computer might only still recognize only 4.
I personally wouldn't do this stuff now with anything less then 6 and having spent quite a bit of time with 12, I doubt I could even go that low anymore.