i really want to play some of mygames on the computer so i can mod and adapt them. however i am unsure whether i should get a desktop pc or a laptop. and if you have any suggestions on which to buy feel free to post them

Get a Desktop Computer. Laptops are nice, and all, but they don't last as long.

what would be the cheapest desktop that could play fallout 3 reasonably well?

Desktops

• are cheaper for any given performance
  
• have less issues with heat, so you can even overclock them
  
• are easier to fix
  
• are more durable
  
• can be built yourself to save even more money
  
• allow for nicer keyboards, mice, monitors, and audio (laptops do too if you game at your desk, but then why are you getting a laptop?)

Laptops

• are portable

Me, I wouldn't want to game while on the move or away from my desk anyway. I've tried before and it isn't pleasant.

I recommend spending around $750 if you plan on building it yourself (I recommend you build it yourself). It would most likely be more if you want pre-built.

And of course desktops are better in terms of performance.

Depends on deals and where you buy it.. I know I can get a computer that can run Skyrim for around 300-400 US dollars... So maybe something like that.. But if you truly want a great gaming computer to run it the best it can be then it'll be more expensive, for sure.

would the new dell inspiron desktop be up to the task?

Give us a product page or a model number.

Try building your own, it's much cheaper, if you don't know how to do it, I'm sure a friend or some relative might know.

Or if your friends or relatives have the "touch of death" when it comes to 'Puters (like mine are) I'd recommend either
http://www.cyberpowerpc.com/
or
http://www.ibuypower.com/