Any errors are too many errors. Replace the bad memory. Or If you have multiple strips of memory you may be able to remove them one at a time until you find the bad one. Really depends on your exact hardware configuration, but some 4 gig systems will run just as well with 3 gigs (since many versions of windows including XP don't use the 4th gig anyway). Or a notebook with 2 sims may run OK with just one, just have less memory to work with. But some good memory is a lot better than a mix of good and bad.

This really isn't an XP forum, but you might well find that XP works OK after you can pass memtest. That is not certain, as the bad memory may have caused the registry or other things to become corrupt. But you might luck out.