Problems with hanging at restart

I recently had my machine reinstalled with Win XP Pro SP3 and now for some unknown reason,I can shut down and start up normally but I cannot restart
normally or after a software update(i.e. regular like Adobe or Windows updates).
The computer will just go from "Logging Off" to "Windows is shutting down" then I hear a beep,sometimes a long one,until I hit the power button wait a few minutes and then do a hard reboot.
What could be causing this? Is it hardware or software?
Please help.

 

Shutdown issues are generally caused by a program and/or process that is refusing to exit gracefully. The program and/or process can be from malware or can be legitimate (such as an invasive antivirus like Norton or McAfee). If you are using a Norton or McAfee product, uninstall it and replace with a better program such as NOD32, Kasperksy, or Avast (free). The Windows Firewall is adequate for most people. Shutdown issues can also be caused by old/poorly written drivers so make sure all drivers are updated, particularly on Windows Vista and Windows 7.

Make a new short cut and paste this in and then click "ok". %windir%\system32\shutdown.exe -s -t 0. Hope this helps!!!!