Compaq presario 5000 desktop series my hard drive is 20GB SDRAM 128MB CPU intel Celeron 800MHz Bus speed 100MHz, windows 98 DC rom. HOW to speed it up windows 98. will Registry Cleaner work

I use an Compaq Presario SR1103WM when I'm at my Dad's house. We've had it for about 2 or 3 years, and used it for everything from games to internet to whatever you can think of. However, it's outdated now, but I can't afford any major upgrades or to buy a new computer right now, so I'm trying to figure out how to run it better. The only specs I know are:

248 RAM (8mb is diverted to video memory) max is 1 GB
Intel Celeron(P) 325 2.56 GHz
40 GB HD

I have no clue about what the video card is, I've had it 3 years and still can't figure it out. Sorry the specs aren't very informative, but you could probably Google the rest if you need it. Right now it's on a dial-up connection, which I only use for instant messaging. Like I said, as of right now I can't really afford to upgrade it, but here in about a month I can. We're also getting Road Runner for it, which should speed up the internet connection a bit. Besides upgrading it, what else could I do to make it faster?
Also, I have deleted a lot of old software that I don't ever use anymore, and I just figured out how to clean the hard drive, so I did that for the first time in 3 years and it is sped up slightly.