Windows 7 32bit on Dell 9200 4 GB RAM 2 x 500GB HDD ... with all OS updates. Been working fine ...booted up, used for an Hr .. left PC running, returned to it, power on but screen was 'black' Had to power off to reboot - on start up (normal) desktop paints in, the spinning wheel runs for ages, then eventually all seems fine ... but can't do anything, only action is cursor .. nothing clickable. (incl Ctl+alt+del) HDD led on PC running permanently. Reboot in safe mode ... chose system restore .. and it shows a Windows Critical update restore point .. at a time that matches failure. ?? OK tried restore ... still the same. Tried Windows 7 repair disk, again selected restore ... Tried restore to next previous (2 days ago) all seems to go well, get login, desktop paints in ... then screen goes black ... all that is on it is cursor. The only other points I can think of is that this morning (last successful boot up) it brought up a pop-up "Express files updated" with recommendation to run it ... as it gave no program, or manufacturer ... I chose not to run. On one of the boot ups during problem .. an unfamiliar icon showed on desktop ... "Homegroup", a green sphere, surrounded by 3 orbiting blue spheres" although not been there on any subsequent boot up. Any suggestions on next step ?