hi i just had a question about switching motherboards with a dell xps 420 i recently purchased, i was wondering if a new motherboard would be compatible with the other dell parts as well as the dell case that i have, i want to be able to overclock and run sli, i just want to know if i can just swap it out and be fine

If it currently has an ATX mobo, then any board should fit in the case. Check the standoff holes in the case to make sure you can match to the mobo. Dell has been known to use proprietary PSUs, they will cross the wiring and they don't put in the best PSUs, so you would have to check on that, probably call Dell. Also make sure the it has a standard size PSU. If I were doing this and the case would handle a standard size PSU, I'd get new one along with the board. The problem with Dell and other mfg is that they get proprietary about things, which sometimes makes it difficult to update. The CPU itself shouldn't be a problem.

The XPS 420 uses a BTX style board, there's no changing it.
All of the components will work with a new board, even the power supply, if you can find a case that would fit it.

You might be able to get a motherboard from a higher-end Dell that is BTX and SLI-ready. Maybe an XPS 720 motherboard will fit in the case.

The MB in the 720 is tray mounted and of slightly different configuration, won't work.