srry but whats socket 775? the type of fit? if so would the i7s fit in with my motherboard pcie ?
The cpu socket.
No, the I7's wouldn't fit on your board, they're socket 1366 ( I7-9xx ) and 1156 ( I5's and I7's )
Your Dell is fully upgradeable, so another ATX motherboard would line up in the case without a problem.