Windows 7 PC Reboot and select proper Boot device error?

[ninjasolidsnake]

On my Windows 7 PC, after an hour or so I get an error where First everything becomes unresponsive, I then get a blue screen and then I get a black screen with this message "Reboot and select proper Boot device or insert Boot Media in selected Boot device and press a key"

I have no ******* clue what is going on. I can use the PC again if i manually restart it but I want to now if I can fix this error and how?

I've tried clearing the CMOS but that doesn't seem to have done anything.

Also i'm not very PC savvy so I may not get some of the terminology.

Cheers

 

[gillywibble]

Sounds like you need to do a repair install.

After the BSOD, does Windows boot normally? If not, check power supply and SATA cables.

Also check temps and if necessary, check HDD for errors.

 

[ninjasolidsnake]

It boots normally if I switch it off and on using the power button.