Well, here's what I'd try.
First, here's the latest graphics drivers for your cards, just in case you don't already have them installed : http://support.amd.com/en-us/download/desktop/legacy?product=legacy2&os=Windows%20XP%20-%2064&RenderOnServer=true
Download MSI Afterburner and Kombuster here: http://event.msi.com/vga/afterburner/download.htm
After you install Afterburner and Kombuster, launch Afterburner. There is a K icon in the main window (on the left side I believe). Clicking this will launch Kombuster. Run one of the tests in FULLSCREEN at your main resolution. On the left should be an area describing GPU usages and temps. Keep an eye on temps and ensure GPU usage is at a solid 99% on both cards. Most importantly, make sure you can run the stress test stable. Keep an eye on the ball/whatever the object is looking for artifacts. If you can run the program for a good half hour without crashes, have reasonable temps, and your usage is at 99% for both cards, your CrossFire setup is stable.
Afterburner will allow you to monitor temps, usages, fan speeds, voltage, clock speeds, memory usage, frame rates, etc. you can also enable in game monitoring.
Hope this helps.Edited by axizor - 11/24/13 at 3:16pm