UBCD! good thinking! i've forgot about it totally. Although you could have driver problems with it. At least the version i have is quite old.
As far as linux goes, i also do not know any advanced way to stress the system. Usually i go through different apps and games that are come with it and see how the system behaves. Some distros have some kind of stress tests (3D, CPU, MEM, disk ) included. Did not do that for some time so could not remember exactly which distros. Ubuntu, Linux Mint would be my first choices.