It occurs to me that I have been attempting to answer the question you asked
about RAM, instead of the ones that perhaps you should have asked about the
program that is not working:
What is the program?
Does it say on the box or CD or website that it compatible with XP?
If an old DOS/95/98/ME program, then be aware that it may never run under
XP. But, you might play with XPs patibility modes", if it is an older
program.
If it is a very new program, does it specify a version of XP beyond what you
have, such as SP-2, when you have SP-1?
Does it specify any video card or sound card requirements, and does your PC
meet them?
Does it specify any free disk space requirements and does you PC meet those,
both for the initial installation and for possible temporary files while
running. For example, I recently downloaded a free program from NASA called
Worldwind and that wanted 10 Gig (10,000 Meg !) of dedicated temp space.
Fortunately it let me change that to a lower number, and it runs acceptably
with only 1Gig of dedicated temp.
Does it install without errors? If errors during installation, what are
they? If no install errors, what run-time errors?
Does it require any libraries that are not part of XP (e.g., Visual Basic,
..Net, IE6, etc) These are usually free downloads, but you might have to
personally do the download and installation, since not all programs do that
for you.
Does it require a high-speed CD drive or DVD drive and do you have one?
Does the program CD/DVD have to be in the tray in order to run the program?
Some programs use the CD as a sort of license key, even if they install its
contents on the hard drive.
Are you attmepting to run this program with other user programs running?
Remember, every program uses RAM ! Try closing all programs except your
antivirus and firewall. If no antivirus, get one ASAP ! If no firewall,
turn on the XP firewall ASAP, then think about getting a better one !
Finally, have you contacted the program maker for advice? Sometimes they
can be very helpful. But, as a courtesy to them, please read their FAQs,
common problems/solution, etc before posting a request for help.