1. Download
UPX (Win32 console version)
2. Extract "/upx203w/upx.exe" from inside the downloaded archive using WinRAR to anywhere (remember where, you will need the path later).
3. Start > Run > cmd
4. cd "<path where you extracted upx.exe>"
5. upx.exe -d "<path to the compressed exe>"
The file should now be decompressed and you can edit it in Resource Hacker.