First question. The "games and programs" you refer to. Do you have the original CD's, or can you borrow them again? If the G & P's were installed from someone else's CD's, and those CD's aren't available, your options are limited. AFAIK you can't lift an installed program from a HDD, then re-install after formatting. When you install a program, it spreads little pieces of itself all over the place, changes the registry, etc. Not like a .jpg or .mp3, which is its own entity.
Second question. How were you planning to do a "system restore"? Do you mean wiping the HDD clean and re-installing? Do you have the original Dell CD that came with the PC? There's a lot of confusion about those OEM CD's. They are specific to the model of PC that they came with, because the drivers for the PC's hardware are bundled into those CD's. People keep trying to use them on other models and just make a mess of things.
Third question. Have you changed anything inside? Added a video card or anythign like that? If so, you'll have to do some preparation by finding the latest drivers for that exact card and burning them to a CD so you can install after formatting.
The website that srx660 refers to is interesting. I had no idea you could buy Dell "Recovery CD's". However, you'd want to find a Dell CD for your exact model, otherwise there will be driver problems.
If your old 2400 has never been wiped clean, it probably is due. The hassles will be worth the effort.
Is MS Office one of the programs you don't want to lose? Try OpenOffice. It's free, works super, and even lets you save your work in .doc if you prefer. Hurray for open source!