This should be a five-minute job, and if Dell used the standard mountings it would be. Guess what…
The T1500 has the mounting holes in the standard places for a LGA 1156 socket, but has screw bosses in these holes, presumably held there by a backing plate behind the motherboard. The stock heatsink screws into these with captive screws – springs hold the bracket down. In theory if the bosses were removed a standard heatsink would clip in, but this would require the motherboard to be removed. Alternatively, the screws with the ~2mm stand-off bits (from the old-style green plastic CD drive mounting rails with the anti-vibration mounts) fit and work quite well. Note the stand-off in these is not quite right, so you probably don’t want to tighten them fully – just enough to hold the heatsink down firmly (It’s best to lay the system down so that the heatsink can rest on the processor to fine-tune the position).
(Why not just replace the fan? Because although it’s a standard size (80x80x25mm) it’s a high airflow model. RS and CPC don’t have anything similar with a 4-pin plug. And as a new heatsink and fan could be got for less than a tenner (before shipping charges) from Misco…)
