DW20.exe is the "Watson" crash reporting utility that Microsoft uses to help developers choose which bugs impact real customers the most and therefore need to be fixed first. The .NET Framework is including support for this system for the first time in version 2.0 which will be a great benefit for all. Since we are dealing with the 64-bit version here, and Watson is a non-managed executable, the installer provides both a 32- and 64-bit version, one in the "Program Files (x86)" directory and one in "Program Files". The installer has logic to detect where the "Program Files" should be installed, but due to a missing bit of information, it is incorrect for the 64-bit version and it ends up on the drive that has the most free space.
If you delete these files, your computer will be unable to report crashes to Microsoft that occur in 64-bit .NET processes. I will now explain an alternative that may or may not work in your case.
First, copy all those files from "D:\Program Files\..." to "C:\Pragram Files\..."
Then, so that the CLR will know where you have put in, open the 64-bit version of your registry editor, and change HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\PCHealth\ErrorReporting\DW\Installed\DW0201 to match the new drive. (C:\... instead of D:\...)