Xbuntu test ram bad-Ubuntu 10.10 & 12.04 & downloaded memtest+ 4.02 test ram good

I downloaded Xbuntu 12.10. MD5 and check disk are good. Put ISO on a DVD. Burned at 4x. started loading onto a Dell Dimension 8100 with Pentium 4 1400MHz CPU, 1002.0 MiB ram, nVidia NV44A [GeForce 6200]. Had dual boot with Ubuntu 10.04 and 11.04. Removed 11.04. Started loading Xubuntu, after sometime, a problem, said I had bad USB Jumpdrive and replace it. Using DVD???? I thought I would test ram. When test #7 started ,all red, all ram bad. Checked Ubuntu 10.04, ran normal. I think if ram is bad, 10.04 would give problems. Put in Ubuntu live CD 10.10 and 12.04, their ram test was OK. Burned new Xbuntu 12.10. MD5 and Check Disk OK. Had trouble checking DVD, only checked program. Same problem, bad ram. Downloaded Memtest 86+ 4.02. Ran ram test for 16+ hours,19 passes, ram good. Decided to start over. Another computer downloaded Xubuntu 12.10, not from torrent, but a mirror. Same MD5 and Check Disk, OK. Haven't tried to install, but checked ram, all bad. Using RDRAM. To replace RDRAM is very expensive, but if sure ram bad, I will. Anyone have ideas? Thanks