Still could be a bit of gunk left, what Operating System are you using ? [ like XP, Win 2000, win 98 ] if its XP, go to sytem tools [ click " all programs/ click Accesseries, run down to system tools then onto "System restore" and just follow the prompts.
If still in trouble i would download http://www.5star-shareware.com/Windo...-mechanic.html
Its free for 30 days, it gets rid of system junk, broken shortcuts, removes unwanted programs and a heap of other functions its a real good program and easy to use, it will work on all OS 's [ operating systems ].
I would use " CLEAN" "get rid of system junk", and "check uninstall software" for any remains of Win Pro, then down to "FIX" "fix registry problems", and "fix broken shortcuts".
Probably best to leave the rest of the programs until your son is there to guide you.
Give that a shot and then try your antivirus program again, if still no good download & install Adaware, Spybot search and destroy, AVG free or even the free trial of "AVG Pro"

You may have to stop running your online antivirus, just try it it see, might not have to stop running your own online one.
If you have to, just go to "add remove programs" in "control panel" find your program and uninstall it and then run the others and see what happens then, you can always go back to your own one if you like it better.
Its good to have Spyware Blaster [another freeby] installed all the time as it stops any spyware, browser hijackers, and other nasty pests from installing on you PC, it won't scan and clean, just prevents.http://majorgeeks.com/download2859.html
good luck