monline

There're a number of "tool compilatons" that the maintainers package into a bootable CD image (ISO) that you can also write to an USB drive. Here're the best tool sets that I know of:

• Hiren's BootCD (AFAIK this one is not downloadable from the maintainer's page since the ISO contains a number of not perfectly legal progs)
• Ultimate Boot CD
• UBCD4Win (Ultimate Boot CD for Windows)

The latter (UBCD4Win) is built around BartPE (Bart's Preinstalled Environment), thus it's not an ISO, but a builder that will create an ISO for you (and requires an WinXP or Win2003 install CD during the process).

Each of these toolsets contain utilities for testing CPU+RAM operation. However you should be aware that malfunctioning does sometimes occur only under extreme load. Thus memory testers like memtest86+ will not trigger them since they test only a part of the memory at a time. You need some stress testing tools for the job. Eg. among the Windows tools in UBCD4Win you'll find Prime95 (P95) which is used by many for stress testing CPU+memory. In the original Ultimate Boot CD you'll find similiar tools too, eg. the Mersenne Prime Test.

I already had PCs in my hands that worked normally under regular load, but during high load weird things (crashes, file system corruption, process deaths) started to happen. Memtest86+ did not produce any errors, but using memtester and stress I could determine that the memory modules were the problem (and it turned out they were overheating).