@ollieTP 

Hi,

I think the Archer TXE70UH is one of those USB Wi-Fi adapters that come with a built-in "CD-ROM" drive that contains the drivers for the adapter. 

If the TXE70UH is not recognized as a Wi-Fi adapter, then it is likely recognized as a CD-ROM drive. In this case you have to use the eject button in Windows to "Eject" the CD-ROM drive. After that the TXE70UH should be immediately recognized as a Wi-Fi adapter.

  @woozle 

Thank you but I do not have a CD-rom drive on my PC - too recent - and I downloaded the driver on TP-link website. 

  @ollieTP 

That is not what I meant.

Anyway, the next time your Archer TXE70UH doesn't show any Wi-Fi please check if your computer shows a CD-ROM drive. In case it does, then eject the CD-ROM drive and that should switch the Archer TXE70UH from CD-ROM drive mode to Wi-Fi adapter mode.

  @woozle 

thank you for your help. Do you reckon i will need to do that every time I start windows?

  @ollieTP 

You probably have to do it every time after you have powered on the computer or after the Archer TXE70UH was plugged into the USB port.

Once the Archer TXE70UH has been switched to Wi-Fi adapter mode it should stay in that mode until the computer is completely powered off or the Wi-Fi adapter is unplugged.

I agree this is a rather annoying "feature". 
 

  @woozle 

Thank you so much for your help. Bought it from Amazon, have still a few days to return it, which is what I am going to do. Can be bothered. Thank you again :)