Personally, I'd try getting new RAM for the old Dell.
It would be good to upgrade it from 256MB anyway. 1GB should be plenty, and should make it run much smoother too, since it'll use a lot less paging file.
Newegg.com - G.SKILL 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Dual Channel Kit Desktop Memory - Desktop Memory
RAM really isn't very hard to install, either. It's literally just pulling two tabs to the side to remove the old RAM, and pushing the new RAM in (the tabs will automatically push into place)
Now as far as the admin password goes, personally I'd try hacking it
that shows one method how. Though I probably don't expect you to understand it.
There's also this method:
I Forgot My Administrator Password!
which is easier (but takes more time)
But, it's easy enough to just reinstall Windows. And in the long run, probably better.
If you do both, you could potentially have two working computers.