I'm really sorry for very vague question title, but I don't know how to put it in a better way.
Server is HP ML150 G5 (2gb ecc memory, quad core xeon), and was running Windows 2003 without any problems. After installing 2008 R2 server system is behaving erratically.
After boot, everything is fine for several days, several being from one to two days max. Then, fax service hangs and cannot be killed or restarted. Server manager hangs while collecting roles data. Closing server manager does not work because of modal dialog "waiting for mmc snapin" that loops forever. Explorer also starts hanging and offers to restart if taskbar is clicked.
System is up to date with windows update patches. SQL Server 2008 works without any problems.
Event log shows no errors that could shed light on this. Any ideas on where to start looking?
UPDATE - after installing PES and bunch of other things, nothing worked. If anything, the situation got worse. Print spooler hung immediately after boot, fax service also. I was even so desperate that I replaced modem (ext US Robotics) with internal pci-ex (also from US Robotics) - no change. So, back to drawing board once more, format C:, install Windows. This time I only installed important Windows updates (last time I installed opional also) and PES from HP. So far everything works as expected, hope it stays that way.