I do not recommend reformatting your harddrive and reloading your software. This is a Windows thing. On an older mac it may be difficult to find all your software again.
Best to have greater than 2gig of free space. Many posters to these forums state that you need much more free space: 5 gig to 10 gig or 10 percent of you hd size.
Be careful when deleting files. A lot of people have trashed their system when deleting things. Place things in trash. Reboot & run your applications. Empty trash.
Go after large files that you have created & know what they are. Do not delete small files that are in a folder you do not know what the folder is for. Anything that is less than a megabyte is a small file these days.
"The simple, fast way to save disk space"
OmniDiskSweeper is now free!
This will give you a list of files and folders sorted by size. Go after things you know that are big.
These pages have some hints on freeing up space:
Buy an external firewire harddrive.
For a PPC computer, I recommend a firewire drive.
Has everything interface:
FireWire 800/400 + USB2, + eSATA 'Quad Interface'
save a little money interface:
FireWire 400 + USB 2.0
This web page lists both external harddrive types. You may need to scroll to the right to see both.
Buy a flash card.