Hi,
I would suggest you to check in the BIOS if it is disabled.
Here is the link for more information:
http://windows.microsoft.com/en-US/windows-vista/BIOS-frequently-asked-questions
Note: Modifying BIOS/complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk.
You can also check the mother board manual to know more about BIOS.
If that doesn’t help, then you need to check the connections in the system tower.
Azam – Microsoft Support.
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