All sorted many thanks for quick help. For any others with same problem and are not too computer literate
from memory here's how I did it:
hold down ctrl, alt and delete - this brings up the task manager. in the the manager you'll see a processes tab - click on that. Click on the 'image name' title - that'll sort everything in alphabetical order. Now look for sprtcmd.exe, highlight it by clicking it then click 'end process' - it should now be killed.
Now go to control panel and add/ remove programs. find the program in the list (i think its just called 'dell support tool') and click remove, then reboot. it should be removed. Goodbye dell support which I haven't used anyway 