XPS ONE 20, upgrade video

I have an XPS ONE 20 with the bog standard 3100 intel integrated video card.

What are the upgrade options available for the video card ?

Anyone know what video cards would be compatible, or what type of slot is available inside the machine.

The integrated card is meeting my needs right now, plus it appears to be having problems (lines/fussyness appearing after a hour or so of use)

I have a call logged for that issue, but I would like to know if its possible to an a new card.

Thanks!