disk fragmentation and Protools, I can't record because of hard drive? Options

My mac powerbook G3 suddenly won't let me record in protools. When I put it in record mode and press play it says ' can't perform that function. Disk may be fragmented.'

I have about 900 MB of hard drive space left; I know I need more, but I had been using protools for a while with less.

I opened a new session to try again, and it let me record if I used the crappy built in mic (just snapping my fingers near mic hole.) But it didn't work if I used the sound input port like usual. It gave the same message. When I closed the session-- not having saved any audio at all-- the file took up over 800 MB, with nothing recorded. I threw it away and got my hard drive space back, but I really need to use protools this weekend. Any suggestions? (especially if there was some cheap and fast solution)

Thank you,
jess