I don't think there is a direct conversion.
I'n not sure how PhotoImpact or PSP generate their customer brushes; you could try to put the form of the Photohop brush in a new file (black on white background) with a single click, then you could perhaps use that image file to generate a new brush in PI or PSP.
esha
--- Kein Wind ist günstig für den, der nicht weiß, in welchen Hafen er will. --- (Seneca)