For two mornings in a row now when I turned my computer on, the system got as far as the Welcome screen and then froze. The cursor did respond to the mouse but aside from that nothing worked, not even Ctl-Alt_Del. I powered off, waited, then on again and it came up perfectly normally. Windows XP, fully updated. Is there a RAM test, and/or a disk test, to locate intermittent problems? Or any other suggestions?