Hi,
Is it just using Powerpoint that the ohms symbol does not print our also when your using Word.
It is possible that when inserting the ohms symbol that it is from another font (symbol) and your printer does not support this.
Looking in '97 powerpoint I find no ohms for normal text with an aerial font (I might have overlooked it though). However I do find it in TT Symbol font. Try it in Word and see if your printer can print it. If it cann't then your printer driver/printer needs sorting if it can then look toward the Powerpoint program.
Regards