My XP Pro always hangs up when starting. Have to re-boot 3-4 times before I get in. Sometimes it displays an error message: STOP: 0x0000007E (0xoooooo5, 0x80595F8B, 0xF9E4C384, 0xF9E4C084) Does anyone have an idea what to do?

There can be many issues causing this stop error. Incompatible software.Corrupt drivers, newly installed usb devices.Sound blaster drivers, memory incompatibility or bad module etc. Try uninstalling the odd sized ram stick looks like it might be a 64 mg stick? Then keep switching till you dont have error. Then try one hardware device at a time starting with the one most recently installed.Lot of work. Easy way to do it is use system restore and look and see what is not installed verses what you have now. If system restore does not work you definitely have a hardware issue.

What RobbieD suggests is good, but before you do all that run "sigverif" to see if Windows gives you any hints as to what could be the problem. My guess is an unsigned driver. Sigverif will check all this for you. If the driver of a particular device shows up in the list then disable that device and reboot. If the problem goes away then either download better drivers or don't use that device. If the problem does not go away then start exploring memory and hardware problems.