Mac Forums

Okay, I am a Mac idiot and know nothing about it. But, I was given an old imac 4 from a non profit (about 10 years old). They only ask that I delete EVERYTHING on it and reinstall everything. Problem. I know nothing of these things! The computer is hella slow and can not do anything at this point,it won't even play dvds! Anyway, if you can help with tips I would appreciate it. I only really want it for the sole pupose of putting educational games for my struggling 5 year old- nothing fancy. Don't really even care about internet access. Here's a little more about the machine:

Model PowerMac 4,1
Power Pc 750 (33,11)
Mac Os X
Version 10.4.11
Processor 600MHz
Power Pc G3
Memory 385 MB Sd Ram

Where would I find discs to clear computer? How do I reinstall the system?? How do I clear it completely? I mean a 'Mean Clean'? How do I get more memory??

Any info is pertenant info because I know nothing. Thank you in advance, Lee.