This is like saying "I just found a coin on the ground. It's caked in mud so I can't see what denomination it is. You think I can buy a gumball with it?"
To determine if it can work, you'll need to do two things. First, make sure it supports the right form factor (ATX). Second, dig it out and get the specs off that label.
Just from the probable age of it, I'd say no. The reason is that capacitors age over time, and so whatever power it claimed on the label probably no longer applies.
You should be able to pick up a cheap used PSU for next to nothing. Heck, look for someone upgrading from a Thermaltake 430W unit. Those are ATX 1.3 and perfect for a Duron, plus there should be around 18,000 people upgrading from those things after finding out that 18A is not enough for their new video card.