desktop hijacked by desktop.html

My desktop background is now white and flashes to a light
grey. Right click/Properties on desktop and only get a
general tab - no options to change anything. The address
[URL] is file://C:\WINDOWS\Web\desktop.html. This is the
name of one of the files that I deleted after my pc was
infected by several files containing trojan viruses etc
[e.g. mstasks2.exe, system.exe, wintime.exe etc...] and
my desktop was taken over by this desktop.html and made
up of circa 20 gifs that had been created in
c:\windows\web directory.
 
Try to change desktop background via control
panel/Appearance and Themes - the Display
Properties/Desktop tab is available and indeed shows my
desired background picture, the name is highlighted but
the apply function is greyed out. Selecting ok does not
change the desktop background. Also my desired desktop
background is momentarily visible during windows shutdown.
 
Searching in the registry for desktop.html reveals the
following:-
 
In hive My
Computer\HKEY_CURRENT_USER\Software\Microsoft\Internet
Explorer\Desktop\Components\0 , the keys Source and
SubscribedURL both contain the values
c:\WINDOWS\Web\desktop.html