Thanks Simon Experimenting myself I discovered that if I just disconnect the disc all I got was a message about something like cant find GRUB . Then dead stop. Looking at another site I found something similar to your suggestions so trying that with my recovery disc created when I installed windows 7 , it would not work , the dos command screen kept saying my commands were not recognised , or no such command . ! not recognised, !
I didn't know about the F8 option , something to remember.
In desperation I booted from my original installation disc and discovered a repair installation option which would recognise BOOTREC/FIXMBR, and it worked , so back to Windows 7.
So thanks for your interest and help Eckiethump.