I SET my computer to defrag overnight. When I woke up I FOUND my laptop had restarted itself during the defrag process and now will not boot into windows properly.

I can enter safe mode, as I am now. It will boot windows but does not bring up the login screen. It just turns black after it shows the windows logo.

Is there anything I may be able to do from safe mode other than a windows 7 boot disk, which I currently do not have?Was it running on battery power ? ?...sounds like chkdsk didn't complete.
Boot to safemode...select Advanced Boot Menu/Command prompt...type in chkdsk /r and hit Enter.
Do NOT interrupt it

Actually i just noticed you stated defrag...it shouldn't need to re-boot after that.
Let us know.Hi

Don't run chkdsk /r unless you don't care about your DATA or you have a complete backup.

If you don't have a complete backup now is a good time to do that first.

Then run the chkdsk as Patio suggested, as it could make the drive worse it also could fix it but you won't know until you run it. Hence the suggestion of the backup.

if chkdsk doesn't fix it a windows system restore may and that is reversible.

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I can enter safe mode, as I am now. It will boot windows but does not bring up the login screen. It just turns black after it shows the windows logo.