First of all if this problem only occurred after installing another program,uninstall it,I assume that you/he can get into safe mode.in that case go to control panel,add/remove and uninstall it from there then see if it will start ok.
If not ME has a System Restore which can be accessed from the restore floppy that should have come with his PC.It may also be possible to access it in safe mode but I am not certain of this,see below from microsoft.com :
So what can it restore? System Restore can restore nearly all system-related files, as well as the registry. Keep in mind that System Restore does not save documents or user files at all. In short, System Restore is not a backup utility in any way. How do I open System Restore? System Restore can be opened by clicking on Start, point to Programs, point to Accessories, then point to Systems Tools, and clicking System Restore. System Restore, as we mentioned before, can also be opened from the Msconfig General folder tab.
How does Windows System Restore make a restore point? System Restore creates restore points right after Windows Me is installed; after re-enabling System Restore from when it has been manually disabled; after the computer has been on for a total of more than 10 hours, and idle for at least 8 minutes; when programs are installed (if using the new Windows Installer 6.1 in Windows Millennium Edition); or when the customer manually makes one from the System Restore tool by selecting Start, point to Programs, point to Accessories, and point to System Tools.
When does Windows System Restore not make a restore point? When System Restore has been turned off on Control Panel, from the Performance tab and file system Advanced button, on the Troubleshooting folder tab, and rebooted, it won't be working. Or when you've gone into Msconfig and removed the check mark next to the *Statemgr, or state manager entry, and rebooted. System Restore, likewise, does not keep track of changes in Safe mode. It also does not work when there is 50 MB or less of free space on the partition Windows Me is installed to, or when booting from the emergency boot disk.
Good luck,I hope you get plenty of beer