Would be better than the dell, but could be better. I vote get it instead of the crappy dell.
If you get it, you'd need new RAM (ffs, PC2700 with a C processor? what a joke)
You'd also need a better graphics card. 5200 is horrible
The PSU doesn't look very healthy either.
And is it just me, or there isn't a hard drive?
I don't know if you can cancel... you should be able to, but you have to make sure of that with the company you bought it from.
If you ask me, or anyone else in here, you should buy the parts separate and put them together. That way you actually know what you have in that PC and it would be pretty cheap too. Maybe not as cheap as those computers you're looking at, but you'd need to upgrade a ton of things on those to get them to be "normal" so I vote get the parts separate off a site like newegg.com.