Will not reboot...continues to go back to "We apologize for the inconvenience screen"

Try this:
Since you can get into safe mode, from the Run box, type msconfig.
Click on the "Startup" tab and select "Disable All" at the bottom.
Now try to boot into normal mode.
Since you can run in Safe Mode, Windows is working. Once all the drivers kick in, something is making it crash. By disabling all the startup items, you can see if Windows will boot normally. If it does, you can re-enter msconfig and enable those startup items that work.
Alternatively, you can do a system restore from safe mode back to the time that Windows worked normally. Then figure out what it was that you installed.

First, see if you can run diagnostics from the F12 menu or from the Dell Resource CD and see if the HDD or any other hardware indicates a failure. If you are having a hardware failure, there is no point in trying to fix a software issue until the hardware is fixed.

If the HDD fails diags, replace it. If it passes, then try booting to the XP CD, and see if you can boot to recovery console, and run CHkDSK /R