UserDumps are created when a program crashes. These large files contain information to help you (and Microsoft) debug what went wrong. However, these files are massive and can eat up a large amount of hard drive space very quickly. For example, on my system I restored almost 14 gigs of space. Read on for the details...
Of course, you want to know where these massive files live.
Navigate here to see if you have any:
Why are they there?
The PCHealth folder contains data as part of the Microsoft Help Center Service. The hdmp files are the large, uncompressed dumps from the crashing program. The mdmp files are the compressed dumps that are sent to microsoft.
As these are just files being used for debugging, you can delete them all safely.
If your userdumps folder continues to gain these files, then your system is having problems. Any application that crashes will leave these dump files. You will have to figure out the problem before these files will stop being created.