Dimension 4300 with Windows XP issues

I have a D-4300 with Windows XP Home Edition installed.  Recently, it has developed an issue with explorer.exe.  You can boot it up, click on the username you want to use, and then you get the Windows background with a popup that tells you there has been a problem with explorer.exe and it has to close; giving you the option to send the error to Microsoft, which you cant do because nothing loads up to use.

Any ideas on what the issue is?  I thought about running the repair from the disk, but since the computer was ordered in 2001, having problems finding the disk.  Will reinstall work, or does this machine have bigger issues?  Everything on the machine is factory installed.

Thanks!