Error: Reboot and Select proper Boot Device...

Hey,

Sorry, I am a big noob but I just installed a new power supply 550w, my old power supply's 300w. I think I connected all the cables in the correct locations so after when I boot my computer I got this message.

When I boot, I get the intel screen then
'Reboot and Select proper Boot device or Insert Boot Media in selected Boot device"

I tried my old power supply and new one still the same message. Obviously the power supply is not the problem...

The only thing I can think of is I connected the cables in the wrong place... but... I don't know.. help please...!

1x Long Motherboard
1x 4 pin Motherboard
1x DVD Rom
1x CD Rom
1x Floppy Drive
1x Harddrive

I am using another computer, not mine but I can't do anythong on this thing!

Thanks in advance!!

oh dear

 

Check that you have pushed the hard drive power cables home properly, and reseat the hard drive data cables.
Is the hard drive SATA?
If you enter bios at power up (by tapping, del or F2 or.. key) does the bios report the presence of the hard drive?

Studio T