I just added 128 MB RAM to a Windows 98 system that only had 64 MB.  (I'd just upgraded McAfee from VirusScan 3.1.6 to Security Center 6, the minimum requirements for which are 32 MB.)  Upon install, there appeared to be no problems -- the system started up OK, recognized the new hardware, etc -- but are there other ways to insure everything is OK with it?  Because I have also gotten, a couple of times on shutdown, a fatal exception error 0E (015F:BFF9DBA7), and if it's the memory then I have now only about 10 days to return it.  (Note: The fatal errors occurred a couple of times in the first 90 minutes of using it, while I kept uninstalling/reinstalling wireless adapter software in hopes of resolving the problem I was having with that.  Also, a couple of times notified by McAfee that the Windows sockets protocols were changed or upgraded.)