I am a customer advocate here at Dell headquarters in Texas. I just found this thread and wanted to see if there was anything I could do to help out. I am going to answer some of the questions asked previously, that may have already been answered, from a Dell point of view just to make sure I don't overlook anything that you still need help on. If you have questions on anything I have posted just let me know.
I did a quick check in case I had forgotten one, but I can not find any information about a Dell Dimension 2100 system. I assume this is a typo, but unfortunately your posts don't give me enough information to figure out which model you are actually referring to. With the model number I should be able to give you slightly better information that what I am posting now.
According to the Microsoft Knowledge Base (
How to troubleshoot "Stop 0x0000007B" errors in Windows XP) the 0x0000007b stop error means that something is preventing the normal boot process from working correctly. There are a few different things that could be causing it, and the specific cause will determine which is the best method for fixing things.
Since you got the error when booting from the hard drive, that tells me that either the master boot record (basically, information on the hard drive that lists what data is where) has a problem, or data or files needed by Windows XP are missing or corrupted.
If you haven't already done so, I would recommend setting the boot order in the BIOS (aka the system setup, accessed by pressing F2 at the Dell splash screen just after powering on) to be: 1) Floppy drive, 2) CD/DVD/Optical drive, 3) Internal Hard Drive (might read Internal HDD). This way, you boot straight to the hard drive unless there is a boot floppy or CD in the system. By the way, Dell systems are always shipped with all drives set to cable select. This is done to make installation or replacement of drives by customers easier.
The problems you had booting the computer with the Windows 98 hard drive is because Windows 98 did not understand what hardware it was trying to use, and basically had a panic attack. You might be able to boot Windows 98 into Safe Mode, in which case you could install the required drivers to let Windows 98 talk to the hardware on your computer. The only problem with this is that I don't know whether there even are Windows 98 drivers for your system (if it shipped with Windows XP installed, the chances are very small).
The later posts indicate that Windows XP somehow got corrupted, so it is entirely possible that the reinstall you ended up doing was the easiest method of getting the system working again. The reason it may have worked in the IBM but not the Dell is that the corrupted files were not needed on the IBM, but were required for the Dell to start correctly.
If you can give me the model I can send you a list of the latest XP drivers (and the order they should be installed in), and possibly some other options for fixing the problem. If I had the service tag (or a case or reference number from a previous service call) I can check the history of the system to see if that gives us any other options.
Hopefully this information helps you out.
Larry
Dell Customer Advocate