OK thanks for the reply.
First of all, the thing you call a window is actually just the BIOS posting it's information in going entering into the boot process. Unless you are getting a BIOS management screen (usually blue with a menu at the top and some information telling you what it is), then the BIOS is getting the hardware to move on to the operating system. If you ARE getting that BIOS management screen, it would stay there and you would probably know what it was!
So the screens of information you are seeing, probably in white text on black background are merely some reports on what is happening. When they disappear and then seem to reappear, this is usually Windows XP trying to start and failing. Often, if you watch very closely, you will see that the white text on black didn't actually change - Windows merely blanked it out for a while but it was there when Windows gave up.
If you WANT to know what is on those screens but they flash past, you can try to hit the Pause key (top right of keyboard). That will usually stop everything until you hit some other key and will not affect anything except make it all wait for you. But you probably don't need to know what that text is.
Randy_Y50 suggested hardware and your tech people said disconnect the external drive. Have you tried that AND made sure anything that doesn't need to be plugged in is unplugged? Unplug EVERYTHING you have plugged into USB ports except keyboard/mouse (unplug webcam, USB memory sticks, even the leads that you might keep plugged in with nothing on the end like a digital camera connector).
If that still doesn't help, get into Safe Mode and try to Restore your computer to a time when it was working. If that works, read some Help to see what else you have to do (like reinstall any programs/devices you installed since that Restore point).
If THAT doesn't work, use Safe Mode to undo that Restore operation and try another Restore point and repeat.
If that doesn't work, get in Safe Mode, undo the last (unsuccessful) Restore operation and then click Start - Run. Then type msconfig and click Run. Select Diagnostic Startup. This will achieve much of what Randy_Y50 was suggesting. It will only allow the most basic things to load but more than Safe mode allows. If while you are at that System Configuration Utility, you click Help and read a little, you will see that you can restart in Diagnostic Startup Mode over and over - don't USE the computer if it starts OK, simply change the settings on the Startp and other tabs in that Utility, making a note on paper to try starting with different things until you FAIL to start again. Once you get there, disable the thing that is stopping the boot and enable the rest. If it restarts, you then know what is wrong. (This is all much clearer if you read those Help explanations of the Diagnostic process.)
Once you know what is stopping your computer starting, you can come back with more info OR tell your tech people THEY should have done that!