I just replaced my power supply on my dell running xp and when I boot up all i see on the screen is reboot and select proper boot device or insert boot media in selected boot device. Any idea why this is happening? I'm pretty sure I put all the connecting wires back to same place I removed them (the new power supply is exactly like the old one) Please help
1) You didn't reconnect the hard drive correctly or the connection is loose
2) Your BIOS reset itself to factory settings and the DVD drive happened to be first in line for boot priority.
To check for the first problem, go into the BIOS and see if your hard drive shows up at all in the list of devices. If not, it's probably not connected.
If the hard drive is showing up, it's the second problem. Go into Boot Priority and move the hard drive to the top. (Note: In this case, it's probably also worth physically replacing the battery on your motherboard. The main way the BIOS gets reset to factory defaults is when the power is interrupted. The battery is supposed to prevent that, but if it's dead, the BIOS will get wiped anyway. If this happens right after changing the power supply or unplugging the computer from the wall to move it, that's usually a dead giveaway. Especially on a machine several years old, which I'm guessing is the case if it's a Dell running XP.)
before the machine tries to boot the operating system from a hard drive, it should give you a POST screen for a couple seconds and at the bottom it'll say something like "press F2 to enter setup" (or sometimes F10, DEL, or whatever other key really). You can't get to the step where it says "select proper boot device" without going through the POST screen first.
Anyway, press whichever key it tells you there, and you'll get to the BIOS.