Once your information appears, right-click within the dialog and choose Select All, right-click again, and then choose Copy.
This isn't as user friendly as it could be, so thought, why not add a "Copy to clipboard" button?
So this doesn’t get missed, copied it to the general steam client place http://steamcommunity.com/groups/SteamClientBeta/discussions/1/828934724126437871/
The 11/5 client beta adds a copy-all option to the system information.
Nothing extracted yet.
This isn't as user friendly as it could be, so thought, why not add a "Copy to clipboard" button?