This is a SFF(small form factor) Small case? My main computer is a Dell optiplex 745.. But it is a tower.. I work allot on these computers and You might just want to change cases or customize that case with more fans..
Those are the same has the Compaq and HP, which also over heats.. They are a good computer, But designed wrong..
Allot of Dells cases are BTX, and some are ATX. the difference is the way the motherboards bolts… on the left side of the case or the right side… I was asking because you could just change cases..Change from SSF to Tower..
Looking straight at the front of the case, The left side would be BTX, the Right side is ATX.. It is more than likely a BTX Motherboard, You would just have to find a tower case the supports BTX motherboards. Gateway cases are BTX and HP make some as well. Do a Google search for BTX tower cases.