While in the process of composing an web-based email today via Internet Explorer, I noticed something odd when I went to attach a file to the message. In the IE file upload dialog there were a series of files listed on the desktop that I knew were not really there. Judging by the dates they had been hanging around for some time now but I had never noticed them (and, no, they were not hidden or marked as protected operating system files):

The files themselves were no mystery; they are nothing more than text files that dump process, thread, and stack information to the desktop when the JRE crashes. I tried to attach one of these to the web message but nothing would happen. However, from within in the dialog box I could right click and open them like any other files. Attempting to move the file also failed because the file itself apparently didn’t exist:

If that was the case, I should then get the same message trying to copy it back to the desktop. Instead, the dialog this time indicated it did exist:

I wondered if I could access these ghost files from outside IE by, for example, attaching them to a message in Outlook. Not surprisingly, the same set of files did not appear from the desktop location:

This was likely something specific to IE. To determine where the files were actually residing, I turned to Process Monitor, started a trace for file activity and proceeded to open one of the ghost files via the IE File upload dialog box. Afterwards, I stopped the trace and did a search for the file in question.

There was half the mystery, the files actually resided in C:\Users\username\AppData\Local\Microsoft\Windows\Temporary Internet Files\Virtualized\C\Users\username\Desktop. The other half of the mystery was then just a matter of some quick research into IE and Virtualized folders. That lead me to this MSDN article Understanding and Working in Protected Mode Internet Explorer. In short:

A Compatibility Layer handles the needs of many existing extensions. It intercepts attempts to write to medium integrity resources, such as the Documents folder in the user profile and the HKEY_CURRENT_USER registry hive. However it will not intercept writes to system locations like Program Files and HKEY_LOCAL_MACHINE. The compatibility layer uses a Windows Compatibility Shim to automatically redirect these operations to the following low integrity locations:

• Documents and Settings\%userprofile%\LocalSettings\TemporaryInternet Files\Virtualized (pre-Vista)

If I unchecked Enable Protected Mode in IE the virtual files no longer appeared in the file IE file dialog. Not that you don’t want to do that, just delete the files instead.