Well, if he's using some non-atx case (micro atx, btx, itx, etc), its really his responsibility to tell us. In fact, its the user's responsibility to provide full information whenever they come here, or anywhere, for help.
We do provide pointers on what to include when you're looking for help, but I reckon common sense is dead: if you're having problems with your fans, we don't need to know what processor they use, and they should know to include all relevent information about the fan (brand, model, where its plugged to, etc).
But we're really nice guys, so we just ask them nicely, and help them out.
About the heatsink, I believe in the adage, size does matter. Go for the BIG heatsink
. If you're cramped for space.... I really don't see how you can still be cramped for space with the 7700, they use those for micro-ATX!!! If you're using something smaller than that, you can forget about all these aftermarket heatsinks anyway.
In the case that the 7700 doesn't fit, then go with the 7500. There's another better heatsink at that size, but I can't remember it off the top of my head. I consider the 7700 the smallest heatsink I'll ever use (aftermarket, post P4).