I recently shot a roll of kodak 200 (36 exposures) and got them developed on the high street and all 36 shots have been exposed onto one frame, shown on the attached image; all other 35 frames are blank. What could have caused this? I loaded and unloaded the film as usual but am using a borrowed K1000. This isn't the first time this has happened so could really do with some ideas as to why this happens.
Well, it seems obvious that the film did not advance between shots. Whether that's because of user error (film not installed right so it didn't catch on the advancing mechanism) or a hardware issue with the advance mechanism not working properly can't really be determined without more information and/or inspection of the camera...
Try taking a couple shots with the back open and no film in, and watch the takeup spool when you operate the film advance lever to see if it looks to be operating correctly. Assuming that particular model allows that, anyway - might need to locate and defeat a microswitch or two to make the camera think the back is closed and/or there's film installed. I'm not familiar with that model, so I don't know...
Doing double exposures with the k1000 requires that you cock the shutter using the lever while simultaneously holding down the release on the camera bottom. This allows the shutter to cock while not advancing the film.
Check to make sure that this release button isn’t sticking in.
Like twalberg says, it seems obvious that the film did not advance between shots.
Make sure the film advance mechanism is working properly. When you have no film loaded, open the back and check that both the film take-up spool and the sprocket teeth both turn at the same time when you work the film advance lever. The sprocket teeth should turn, even if you try to (gently) hold them back with your finger.
A couple of other things to check:
Like Hueco says, check that the sprocket release button on the bottom of the camera is not stuck in.
Take a look at the developed film (the strip of negatives), looking for ripped/damaged sprocket holes.
Also make sure you are loading the film correctly. I came across this manual for the K1000. Page 10 explains loading the film.
When loading the film: after threading the leader onto the take-up spool make sure the sprocket holes on both sides of the film strip are actually aligned with the sprocket teeth before closing the back. Note that the film leader goes under the take-up spool. If you get this wrong the first frame advance will undo your film threading and the sprockets won't engage.
Remember that you should move the film advance lever its full distance to make sure the film advances one full frame between shots.
When you cock the shutter/advance the film, the rewind knob should spin as it is unwinding film.
If this is not happening, be sure the button underneath the camera to release the advance spool is not stuck and or check to be sure your sprocket holes are lined up with the advance spool and they are not tearing the sprocket holes.