stuck on blue dell screen during startup

You do not say what things you have tried, so I may be repeating one of their suggestions.  Boot from the XP CD (you may have to change boot order in BIOS setup - F2 during first boot screen, or press F12 to go to a boot menu which may contain the option).  Then after things load, on the first screen choose Recovery Console; if you have not set up a special password for the Administrator, then select your present installation of XP for repair and just press Enter when it asks for the password.  Then run FIXBOOT; your boot files may be messed up and that would fix them.  If XP is your only operating system, then you can safely run FIXMBR, in case that the master boot record is messed up as well.

finedonna,
If your system is not moving past the Dell logo screen then it's not completing the POST ( Power On Self Test). Unless your system is very old there will be four diagnostic lights on the rear of the tower. The next time you start your computer and it hangs at the Dell logo check the status of these lights and include what color they are when you post here again.

Thanks for such a prompt reply.  I have windows 98 though, not xp.  Dell has had me unplug the computer while stuck on the screen.  Hold the power button in for 10 sec and then restart.  It works sometimes but can't keep doing that.  We've defragmented and ran some diagnostics.  Now they want me to load the operating system again and that seems too major.  My kids don't want to do it yet because of all the backing up it requires.  Maybe it is necessary but we really haven't done much else yet to solve the problem.

If you have anything else on the back that lights up, like an ethernet and some other pci cards, the lights you want are somewhere around the printer port, are marked a,b,c,and d, and they are usually green. If there are any amber/yellow ones that four-light sequence indicates where in booting it got hung up. Your system manual should have explanations of those sequences too.

Another thing you can do is as soon as the splash screen comes up, hit escape to minimize the Dell screen and see the boot tests it's doing under that screen, and see if you can catch exactly what it's doing when it hangs.