What do you mean by "I got it to work in Win NT only.." ? You mean you've already done that task on WinNT, and need the batch file to Win9x, or you need the batch only for WinNT?
I think that in WinNT you may use FOR/R:
FOR/R C:\ %%F IN (*.PST) DO DEL %%F
That actually command works for Win2000, I'm not sure it will work on WinNT. That command line is for using in a batch file. If you desire to type and enter it directly on the prompt, replace "%%F" by "%F".
On Win9x it's a little more difficult. Visit the following URL:
http://groups.google.com/groups?hl=pt&selm=a45gl1%241c94t9%241%40ID-55970.news.dfncis.de&rnum=5
This is a post from Willam Allen, which the script you need (that would be the first script, there are two). It's a great script.
-- Secret_Doom - Leonardo Pignataro --
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www.batch.hpg.com.br