I have one of those little problems that ends up being an expanding PITA. I have a cheap dial indicator, 0-1" in .001 increments, 10 rotations. Mine doesn't have a brand name on it, but it looks more or less like this one. Some time ago, I noticed that only one of the tiny screws holding the back on was there, and I took it off the bench before the last screw went to a parallel universe. I went through every small screw I have and nothing fits.
I want to put it back together. Trying to get accurate measurements on a screw that measures across the threads at .076" and is .150 long is difficult for me, even under magnification. Then I remembered we have a USB microscope that I got some time ago. I could measure the pitch by counting thread turns under the microscope. I'll just plug it in right here...
And it won't work on my computer. Go to Windows Update and get the latest driver version. Then I find Windows Update isn't working. So the troubleshooting begins. Microsoft has a support page for troubleshooting failures in Windows Update. It had me type about 80 lines of commands into a Command (DOS) window and I found about 15 .dll files that are bad or missing.
So since I need Windows update running more than the microscope itself, I need to go troubleshoot that.
Then I can get back to the problem that started this cascade. Measuring across the peaks of the thread, the screw looks really close to the M2x0.25, but the pitch is wrong. By the pitch it looks more like a #1-72. Neither of those are common screws that I could just find locally and try.