I came home from a weekend away to discover that my PC had rebooted and the screen showed the above message, presumably after a Windows Update. The options were to Escape or Continue.
I tried to Escape and ended back here. I inserted my Rescue Disc, which had worked on a similar occasion. The boot screen appeared but when I hit return I ended up back here. I tried the Windows 7 Disc with the same results. I Googled the problem, most of the advice led me down the same road, with no resolution of the problem. I tried turning off and back on using the button of the front panel, sill no luck.
In desperation I turned off the computer using the On/Off switch on the power supply unit on the back of the computer. I left it for a bout 3 minutes and then turned it back on. Magic it Re-Booted and started normally.
Now't so weird as computers...