WIN7 BSOD REGISTRY_ERROR, ntoskrnl.exe, Bugcheck code: 0x51

Unfortunately, i couldn't restore a safe point because i don't have one (I keep forgetting to create one)

Windows automatically creates restore points, but only if you enable the facility.

You might be able to fix the problem by restoring a backup copy of the registry. The process is involved and requires some careful typing. Ask a computer-savvy friend to assist you if you lack experience in this area. Note that it might reset your password to an earlier value.

1. Press Shift+Restart to force Windows to boot into the Repair Menu.
2. Select Advanced Options twice.
3. Select Command Prompt.
4. Select an admin account to log on.
5. Enter its password and select the the appropriate keyboard layout.
6. Identify the correct drive letter for your Windows installation. It could be a drive other than C: but it won't be X:. You do it by typing these commands and pressing Enter after each:
    dir C:\Win*
    dir D:\Win*
    dir E:\Win*
    until you find the Windows folder.
    I shall call this drive "Q:" even though it won't be Q:.
7. Type these commands and press Enter after each:
    cd  /d  Q:\windows\System32\config
    xcopy  *.*  Q:\MyRegBack\
    cd  RegBack
    dir
8. Examine the dates of the Software, System and SAM files. Were the files created before or after your problem became apparent?
9. If they were made before the problem became apparent then you can type these commands and press Enter after each:
    copy /y software  ..
    copy /y System  ..
    copy /y Sam ..
    (the two dots are part of each command)
10. Reboot normally. If things do not work out then you can backtrack by copying the original registry files from Q:\MyRegBack to Q:\Windows\System32\config.