Yes, A G4 (running OS X) can read from a PC hard drive formatted either with Fat32 or NTFS. It can only write to a FAT32 formatted drive.
The easiest way to do this would probably be to get an External USB drive enclosure, and slap that drive into it. Then you can plug it into the G4's USB port as necessary.
The cheapest way to get a new macintosh is to get a new Mac Mini, which runs $500, but you need to supply a USB mouse and keyboard, and monitor. These are Intel-based, and they also run Windows just fine if you like. I have one of these in my lab, and it works great for non-gaming usage.
If that's too much dough, then you're looking at a used Mac. The lowest one you'd want is a so-called is a "Grey G4," or any tower with a G4 processor and AGP slot (if it only has PCI slots, pass on it). I would expect you could get one for $250 on ebay, but it would be used and without a warranty.
Hope this helps,
Llama
