One, unless you picked up an ancient hard drive, you cannot get an ATA drive in 18GB (is it a 20GB drive?).
Two, reinitialize it as one partition (use HFS+) and install OS 9.2.x onto it. Update right away to 9.2.2 as well as all the other updates that come up with the Software Update control panel. Since you don't have firewire, forget about the iPod updates as well as the ones for authoring (burning cd's).
Three, boot into 9.2.2, insert the OS X install cd and double click on the installer. Let it install to your hard drive and reboot.
Since you will have just wiped the drive, you shouldn't have to worry about fragmentation. If it still refuses to install all the way, or properly, I would suggest getting hold of that mook that installed the memory for you and get some quality memory installed (Kingston is good stuff). Make sure it is PC100 (or PC133) and CL2 memory (all 222 would be ideal). You could also attempt installing with just one of the memory chips installed, since one of them could be on the way out, but I doubt that. If the memory comes up as two different CL ratings, that could be the problem right there. There was a time where having two different CL rated memory chips installed gave the system all kinds of problems. Most of the current memory has gotten over that problem, as well as the latest firmware updates (for G4's and the slot loading iMac systems).
You could also double check the cables connecting the drives to the motherboard to make sure they are firmly in place.
You also might need a new battery on the logic board (1/2AA size, 3.6v Lithium-Ion battery). Those can be found at most/many Radio Shack's. They say right on them... "For Apple Macintosh Computers..." The Radio Shack part number is 23-026 (I have one right here that I am looking at). They generally run about $10-$12 and last several years (typically, they don't start to go until at least 3 years have gone by on the computer). You could replace the battery before calling on the memory... Just to cover your own ass.
IF you are going to get Norton, get the latest version... NSW2, since it includes NAV (for both OS 9.x and OS X).