|Sorry, I should have phrased my question differently & asked for either the make/model of the board or make/model of the system. I know it's a Compaq Presario but would need to know the model number. I can take a stab at it based on what you provided though. Presario 5400 series?|
The max amount of RAM it can handle is 512MB, 256MB per slot. You're already there. Your system *should* run reasonably well with that amount of RAM so it's likely your system is bogged down with a lot of accumulated garbage...especially if you don't regularly dump temp files, history folder, temp internet files, etc. You may also have a lot of unnecessary programs loading at startup.
Try installing a program called CCleaner-Slim & use it regularly. I suggest you uncheck the box next to recycle bin (you can dump that manually as needed) & if you have passwords saved for various websites, e-mail, etc, uncheck the box next to cookies. Then run both the cleaner & the registry scan - delete everything they find.
CCleaner -Slim, direct download
You should also run MSCONFIG & disable any startup program that isn't absolutely necessary.
How to use MSCONFIG in Windows XP