We have several HP ProBook 6550b notebooks in our organisation, and one of them is having a serious problem.
While working on it, it very often freezes and locks up. The mouse cursor won't move anymore, numlock/caps lock don't do anything, ctrl+alt+delete doesn't do anything and there is no error message on the screen. All I can do is turn it off by holding the power button for 4 seconds.
I've ran all the system diagnostics from the BIOS (Start-up test, Run-in test for several hours and Hard Disk test) and they all passed.
I also updated the BIOS to the latest version and performed a full reïnstall of windows 7, but it keeps locking up.
I also did a static discharge.
I've brought it into the shop where we bought it (a HP preferred partner with it's own repair department) and they did pretty much the same as I had already done (ran tests, recommended reïnstall,...)
Today I did another reïnstall of windows 7, and I got to install service pack 1 and the drivers, but after that I tried running Windows Update and it froze again. This has happened 4 times in a row now. Sometimes it even freezes before windows has booted up. It also happens while working on it (office files or browsing the web)
How do I proceed to troubleshoot this issue?
Could this be a faulty motherboard or cpu?