In the old-line IBM PC PSU's, there was always a big label on the
outside 'No user servicible parts inside' and a non-standard screw
sealing it. Every one that I've opened had a socketed fuse inside.
Sure.. And you'll find that if that fuse blows there are almost certainly
other component fialed as well (most likely the chopper transistor or one
of the mains rectifier diodes).
-tony