You can make a Windows PE disk:
if you need something in a quick pinch, look up UBCD4Win. Has some limitations dealing with w2008 but will get you start quickly.
With it you can verify first the hardware such as RAM, th disks etc for HW faults. Once the HW is out of the way you can start looking throught the rest of the system.
You should be able to look at the event viewer from the boot disk. You can also look to see if there are any Blue Screens of Death etc... And if you build you boot disk with an Anti-Virus, you scan the system for that too....
Using safe mode you can disable services, uninstall apps, reinstall drivers etc