Freezes at dell logo

[dan macduff]

i have a dell optiplex gx50 that every time it boots it only gets to the dell logo with the company website below it. also the loading bar only goes 1/4 of the way and then freezes. i've tried unplugging everything except the hard drive and everything external but nothing worked. please help

 

[Ubrales]

Check the Chassis Intrusion Switch.

http://support.dell.com/support/edocs/systems/opgx50/1.2%20GHZ/en_sma/index.htm