Can't give you a specific answer, but here are some things to consider:
1. What form factor is the current motherboard (eg, ATX, custom)? Any replacement motherboard will have to be the same form factor, and presumably have the same mounting holes etc.
2. Dell frequently uses a custom connector between the motherboard and the front panel. The pin-outs for that connector are not usually public knowledge. So any replacement motherboard will have to be compatible with the existing front panel connector.
3. You might have to reinstall Windows on the hard if the new motherboard uses a different chipset driver etc...