My unraid server was hit by lightning (induced through the network cable). It POSTs, but it just resets when it tries to boot any OS. The motherboard is a Gigabyte GA-EP35-DS3R. I don't want to replace it with the same board because those Gigabyte boards have that annoying HPA that can't be disabled. Any recommendations for similar LGA775 boards with lots of SATA ports? It needs to support a Celeron 420 Conroe-L and DDR2 800 RAM.

I highly recommend either the Supermicro C2SEE or the Supermicro C2SEA. Both motherboards are nearly identical. They have only 6 SATA ports each, but enough PCIe slots to support a 20 drive server.  Both boards are highly reliable and should work with your CPU. You may need to replace your RAM, though, as Supermicro boards are very picky.

Thanks for the suggestions! Both of those boards use DDR3 and I'm really trying to keep the cost down. If I have to spend much more than ~$70, I'd probably be better off just upgrading the whole system. I'm hoping to find a decent used replacement on eBay or something. After further research, I'd actually be fine replacing this board with another GA-EP35-* since the latest BIOS has a setting for disabling the HPA. I just can't find any for sale. There are plenty of GA-EP35-DS3L's on eBay, but they only have 4 SATA ports which means I'd have to get a PCIe SATA controller (which aren't exactly cheap either). I wish I could use Newegg's power search across the whole internet .

Actually, the internet says that the GA-EP35-* boards are virtually identical to GA-P35-* boards. The GA-P35C-* boards are also very similar. So that provides more options on eBay.

 

I'm still interested in other suggestions if anyone knows of similar boards that are available on eBay.