So I've seen a lot of people ask questions about compatibility of different parts, "will this ram work with this motherboard", this cooler with that motherboard, will this video card fit in this type of case, that kind of thing. Also people have suggested a system configurator or system checker for newegg. That is a great idea, but it would be very hard to accomplish for a lot of reasons.
But what I was thinking was why not have a feature as part of eggxpert that lets registered users list the components inside their computers as part of their profile. Many people already post this info in their signature anyway. Perhaps list things like part: name part, model number, quantity, etc.
Then people at newegg or eggxpert could search a database of people's computers that are known to work, and see what many people have used.
For example...
If I wanted to get a Q6600 processor and didn't know which motherboard to use, I could search for all computers that have a Q6600 and see which motherboards are used the most. From that I could also check to see if the RAM that I already picked out would also work with the motherboard that I just found from the search.
You could also add in a ratings system where people could rate the parts that they are using in their computer. This could be simple (i.e. stars) or more complex (like newegg's review system). I know newegg has this feature, but it is not looked upon very highly due to the reviews themselves. Or the search results could simply link the existing newegg part/reviews if currently sold at newegg. Alternatively eggxpert could have a separate ratings system that also lets the eggxpert reviews show up on newegg as well noting that the review came from eggxpert (which people might trust more).
Other thoughts...
Allow users to have more than one computer listed in their profile
Either have each system configuration shown be anonymous or show the username so that the person searching could ask a question to the user with the specific configuration that they have a question about (perhaps let users opt-in to have the system specs in the search linked to their profile)
Kevan