|The power going out probably produced (a) power surge or spike(s).|
If your computer and everything connected to it is not connected to something that protects it from that, or sometimes even if it is (e.g. if it was a lightning strike on the power grid that caused the power outage), that can damage anything connected to the computer.
Usually the most likely thing to be damaged is the power supply. Black screening and rebooting is often a symptom of a damaged PS.
You often can't tell there is anything wrong with a PS by removing it's cover and looking at it if it was damaged by a power surge or spike - usually nothing looks burnt, and the fuse in there usually doesn't blow, even if the PS went completely dead.
Check your PS, etc.
See response 4 in this:
The hard drive could be damaged physically or logically, but usually it isn't. However, the data on the hard drive could have been damaged - that can usually be fixed, or if not you can re-install the software.
check your hard drive.
See the latter part of response 1 in this:
If you don't have a floppy drive, you can get a CD image diagnostic utility from most hard drive manufacturer's web sites, but obviously you would need to make a burned CD, preferably a CD-R for best compatibilty, on another computer if you need to.
If you transfer a hard drive that has XP installed on it to another computer that has drastically different hardware - a different chipset especially - and connect as master on the first IDE and boot from it, XP cannot handle the hardware change and will not boot into Windows - that is NORMAL. Often what happens is you get the begining of XP loading, then a flashing cursor on a black screen, forever (XP loads no further). That can be fixed by running an XP Repair Setup, in which case you won't lose any data already on the drive, but if you're just trying to see if the drive is okay you should not do that - that will set the XP installation to the hardware on the other computer. You are better off to just connect it as a slave or as master on the second IDE if you want to see whether the data is intact, or if you want to test the drive.
If the other computer re-booted when you connected the Dell hard drive to it, that could be caused by damaged data on the hard drive, or less likely by a physically or logically damaged hard drive. Run hard drive diagnostics on the drive, same as pointed to above.