If you have a legal copy of Avanquest Fix-It Utilities 8 then
The Product key is on a label stuck onto the back of the box, or inside on the leaflet, or on the back of the sleeve for the disk(s)
If the product key is lost, contact Avanquest support as they may be able to help.
Sounds as though you are missing an "exe." command or file; which is something too complicated to answer here. Since you are trying to install a utilities program, you should know what an uninstall manager program is. Find one of these free uninstallers and download it and it will remove the Avanquest from your computer. At this point, that would be the easiest solution. You can then download Glary Utilities Pro as the recommended replacement to the Avanquest; GUP will then take care of everything for you with a minimum of effort. Trust me.
Unplug the computer from the line connection, pick it up with both hands, carry it to the storage area and put it down on the floor. Walk away, close the door, and return to the computer you are now using. See wan't that easy.
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It's disabled by default. From a recovery console you would need to type net user administrator /enable:yes You could also download and run the hiren boot cd to unlock, reset the password on whatever account is available. Follow this video.