See this free removal guide from Malwaretips (a site who's guides I trust): click here
Also if you want to burn your own W7 DVD to use for repairs etc. you can download the .iso (disk image) from click here be aware that if you want to reinstall you have to use the Dell oem key on the COA sticker on the pc's case. You cannot use the DELL oem factory pre-activated key (it won't be accepted).
Thanks guys, I viewed all possibilities and ended up using Malwaretips. I took the precaution of copying the web page (not necessary). I only carried out step 1 and the PUP has gone. I don't know if I need to use steps 2,3 & 4. Perhaps you can advise, lotvic. Anyway, thank you all very much for your help.