Notes about the XDSL file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The XDSL file type is primarily associated with 'D-Link Router' by D-Link Systems, Inc.. D-Link router firmware updates are country-specific. While some countries use .BIN files, for the 604 router at least, D-Link uses a file with the extension XDSL for UK firmware updates. The file will have a name of the form "wadslg604+R221b3t33au.xDSL" and be in a folder called "Binary_Firmware".