I've had trouble accessing the PRIME95 web-server, and have yet to get it to run successfully once installed. [Perhaps if I'm doing something the wrong way, someone could enlighten me, to save me the troubleshooting time and trouble.]
What I do is to run programs in the background which load up the processor, and I can monitor processor-usage with Task Manager's "Performance" Tab while monitoring the temps with my motherboard's ASUS Probe, although SpeedFan or MBM5 would do just as well. For instance, I have a 1999 version of the game "Asteroids" which does not cause the system to heat up noticeably while the game is in play, but if you minimize the game in a suspended state, it loads up the processor to about 50% usage. In order to get the system up to a rock-steady-solid-line 100% usage under Task Manager, I run a Norton Anti-Virus scan on the whole system with Asteroids suspended and running in the background.
I've run programs like Microsoft Flight Simulator 2004 -- certainly as intensive in processor usage as many games -- but it is so far only the combination of the above programs that get me to 100% load usage -- and the temperatures show it. MS Fright Stimulator pushes the load temps to around 94 or 95F; my other two programs running simultaneously push the load temp to 104F or 40C.
SiSoft Sandra 04 has a "burn-in" wizard which also stress tests the system, and you can watch the temperatures rise through its built-in monitor. But none of the tests in the wizard seem to push my temperatures above the MS Fright Stimulator level . . .