1. Win 10 seemed a bit slow switching tasks; rebooted - got the Dell Logo, then a circle of white dots spinning endlessly. Never proceeded
2. reset to CD boot, tried my Win 10 repair disc; Dell Logo, below was white dots circling and statement "preparing automatic repair". shortly screen blanks, soon after get mouse pointer - can move it around with mouse but nothing proceeds thereafter.
Tried unpluging all devices except mouse, keyboard and monitor, no change.
3. Any suggestions welcomed; upgraded online from Win 7 to Win 10 - if cannot solve this will have to reinstall Win 7 (have disc); don't know if can get Win 10 after that.
4. Have all my files backed up on portable USB harddrive. Lose all installed user software, but have most in download directory on backups.
DELL XPS 8700 - managed to get system test app up, everything tested OK - only ran half-way thru 500GB disk test.
This morning (after percolating (?) overnight there was a recover screen - able to run a system restore to last restore point; completed successfully (it said). Selected reboot, back to Win 10 start logo (4 squares) with white dots circling as before.
Gonna tear out what little hair i have left! <GRIN>