The HD is a little small but nothing to worry about.
10.4.7 will run on this machine quite happily.
I would trash Norton System Works, an oxymoron if I ever heard one, and go with Disk Warrior.
You are using 10.2.6 because you have never upgraded your OS. I'm not sure I follow your statement that you are running that because it works with all the freeware. The statement should be that the freeware works with 10.2 You might consider chunking some of the freeware if you have a ton of it. Is any of it essential? There is a possibility that it will not run on the Intel Mac anyway.
Check Epson for Intel Mac drivers for the scanner and printer.
P
Here's what I bought in 2003:
Apple iMac, G4, 800MHz, SD RAM 1 GB, 80 GB HD, CD-RW/DVD-R superdrive, OSX 10.2.6
Apple Pro speakers
Belkin 4 port hub
Floppy drive (for my Sony Mavica camera)
Epson C42UX (printer for photos - it's a cheapie, but it was free)
HP DeskJet 5550 Ink Jet Printer
Epson Perfection 1660 Photo Scanner (can do slides and negatives too)
Norton System Works (lots of utilities)
Microsoft Office X (word processing, spreadsheet, email, powerpoint, and MSN messenger)
I'm still running with OX 10.2.6, because it works with all the freeware I've added on.
OK, now I'm feeling it's time to upgrade the software. My question is: Can I put OS 10.4.7 on this computer? Is there enough room? I'm thinking of spending about $500 to get an external HD (for backup), Roxio, Disk Warrior, and OS 10.4.7
Do you think I can do this with the iMac I have? And do I really need Disk Warrior?

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