SpyStudio is a user-mode API monitor, a powerful troubleshooting tool which can track what an application is doing - the Registry keys it's accessing, the file's it's reading and writing, any window's it's created, the COM objects it's using, and more. Sounds technical? Yes, but don't let that put you off. Spy Studio works in a similar way to Sysinternals Process Monitor, and if you're happy using that, or similar Sysinternals tools, then you'll be able to use and get at least some benefit from the program.
To get started, you must first "hook" the application or process you'd like to monitor. If the program is running already, right-click it in the Process list and choose "Hook" (if the process is greyed out, that means you're using 32-bit Spy Studio; download the 64-bit edition instead). Otherwise click the browse button next to "Execute and Hook", choose your target executable and click "Play" to launch it.
Having SpyStudio monitor an application means it'll run much, much, much slower than usual, so you'll need to be patient. But otherwise wait for the program to launch, run whatever other tests you want to do with it, and when you've finished, click Analysis > Stop All to end monitoring.
The results of SpyStudio's monitoring are displayed across five tabs. The most straightforward is probably "Files", which lists every file the process has tried to access while it was monitored. You'll see the file name, how it was accessed (just to read, to read and write, to execute and more), the number of times it was accessed, and more. Importantly, any calls which results in an error - the file doesn't exist, say - are displayed in red, so you might want to investigate those first.
The Registry tab provides similar information on Registry keys your program has tried to access. These are presented in a Registry tree, you can browse it to any key or value of particular interest, and again anything that's resulted in an error is displayed in red.
The "Trace" tab provides a full list of all the monitored calls, allowing you to see every Registry access, file read and write in sequence. There will probably be thousands of calls here, so don't expect too much, but it can occasionally be useful.
The remaining tabs are really only useful to Windows experts. "COM Objects" details the various system components your program has tried to use, while "Windows" shows any windows it's created.
We've run through the basics here, which in themselves are enough to troubleshoot many technical issues. SpyStudio can do much more, though. Click "Monitor" and you can choose extra calls to track (Drivers, Internet, Shell, and many others); and if the report is too complex, then the program has a Sysinternals-type filter (Edit > Filter) to help ensure it displays only the calls you need. Very useful.