The easy answer is no. There might be some Windows based stuff that could do it, but I wouldn't try it either way. Get a new motherboard then go for it.
another problem with those factory-built comps is that they use shared video cards. and they then only give you like 256 mb to begin with. also the PSU's are very small. like 200w or so. and they cost hella more than to go and build yourself a monster.
shared video is almost a thing of the past in prebuilts now. but notice it's almost.... i have seen some with shared video... but that means with most modern mb's that there's an open agp slot for you to put a nice piece of hot AGP lovin in the way of a vid card ^_^... and i do agree that there psu's are small... but that's because most people don't do much with their prebuilt, save maybe the lone upgrade for video or ram... but those psu's take care of everything that's needed... plus for those that do want to upgrade, there is always the option of replacing the psu ^_^
I didn't ask anyone for upgrade opinions, I know enough about computers to make those decisions. I am asking is it possible to OC a dell? And I guess it is, thx people