Since you have given sparse information on your setup, we are all having to gues a bit to try to help. If you want a better service, then please give us a chance by letting us gave some idea of the setup of your pc!
If your Duron 600 is as specced from the factory, it is likely to be restricted more by memory than processor power for this job. IBM is rarely generous in memory allocation in ther standard configuration PCs. You could check this by looking for excessive disk thrashing immediately before a lockup – or always during print spooling. One possible temporary solution is to clear the temp folder (in the Windows folder) and then increase the paging file to a permanent fixed size of several hundred MB – try 400 to start with. If this is partially successful (smaller jobs do not lock up, but larger ones do) try increasing memory to 512MB (PC133 memory is cheap these days), but no more as Win 9x will not successfully address any more. Updated Athlon processors are harder to find (your motherboard will probably not accept anything much more than 1 GHz), but you could check ebay if you do want to go that route. That is likely to be more hassle than you want though. Replacing the machine might be easier.
Hope this helps