Read the Registry
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\FileAssociations
the Key UserSid
It should return something like "S-1-5-21-123456789-987654321-1708537768-3320" --> That's the currently logged in UserSid (THIS IS AN EXAMPLE, JUST A BOGUS VALUE!)
On my system, there is no FileAssociations key underneath the CurrentVersion key, so that solution will not work.
In any case, there are better ways to get the SID, I would not go to the Registry for that. For instance, you could use GetUserName() and LookupAccountName() instead.
But there is an even easier way to get the path to the user's Recycle Bin: use either SHGetFolderPath(CSIDL_BITBUCKET) or SHGetKnownFolderPath(FOLDERID_RecycleBinFolder) instead.
Open Explorer, and enter in the Addressbar:
"c:\$recycle.bin\S-1-5-21-123456789-987654321-1708537768-332"
And voila: The usual Filenames to read
The Recycle Bin is a virtual folder. Its content is stored in a database within the Bin, and Windows Explorer uses a Shell Extension to display the contents of that database. The actual information is not on the file system. You have to use Shell APIs to access the Recycle Bin and extract information from it.