The problem with the bios test is that it's still not very extensive and can miss quite a few errors.
The best way of finding out bad ram is (believe it or not) installing windows. if it starts crashing when copy files then when the cab files are decompressed into memory it corrupts them and so crashes.
Alternatively there are numerous memory tester programs on the net.
The problem with windows installation as a testbed for RAM integrity is that the installation can crash for various other reasons too. Thus, it is hard to say tat, just because windows installation crashes, that your ram is bad.