Computer shuts off while trying to boot into Windows.

Another odd one. This is an old 233mhz Win98SE machine. I use it for odd jobs. It worked fine a few days ago. Now, when I try to boot up, it starts to run windows, then shuts off the power. I can't even boot to safe mode. I can, however, boot to the command prompt. I can do a DIR command or any other DOS command. I can even go into the Windows directory. Scandisk runs ok. If I type "Win" or "win /d:m" (Safe mode) I get a little bit of hard drive activity, and then power off again.

This is an actual ATX shut down. Anyone ever seen anything like this? Any ideas on what to do?

Thanks.

While I'm not a computer tech I would suggest a new power supply might be needed.