|First thing I would do is check the monitor both power and data connections... these can come lose if they are not screwed in or screwed snug enough. |
A virus can cause similar symptoms if it infects the BIOS... so just in case, reset the BIOS removing the BIOS button cell battery for five minutes. That will erase the virus or BIOS corruption that may be causing the problem..
If it doesn work after that, check all power source connections to drives and motherboard, and also check data cable connections. It could be that moving the computer caused some connection to come lose.