I think the best site for this is www.wincustomize.com . Download from there WindowsBlidns, ObjectDock, IconPackager, BootSkin, LogonStudio & a few nice themes. That's my way of making mac from pc.
A quite old topic, but maybe someone'll find it helpfull. So, u need to change default value of key "HKCR\exefile\DefaultIcon" to location of icon you want (%1 means an icon in *.exe itself).