Insert Microsoft Windows Vista Installation Disc.
Press any key when it says "Press any key to boot from CD".
After that you should see "Windows is loading files..."
KEEP pressing F8/F9(can't rmb which, just press both alternately) while the progress bar loads..... Dun let go until you reach "Advanced boot information" where you should see Safe Mode, Safe Mode with Networking, Last Good known configuration etc...., just select Safe Mode with Networking(or Safe Mode/Safe Mode with Command Prompt) and press Enter. Wait for the files to load and there should be "Safe Mode" on 4 corners of your monitor.
Just be patient and wait. A windows would soon pop up and says "Install Windows". Don't worry, click next. Now at the bottom of this window, you should see "Repair Windows". Click on it, and there are several options available here. For this case, which is "Bootmgr is compressed.", CHOOSE THE LAST OPTION - "Start Command Prompt".
OK type these things (Only works if you have Firefox, can't think of anything else) below and follow closely:
When Command Prompt is started, type the command below first to ensure that C Drive or whichever drive which contains all your system files is selected:
X:\System> (The string on the left is what appears on command prompt, may differ on other computers.)
Now TYPE "C:" or "D:", depending on the hard disc volume you are using...
SO IT BECOMES:
THE RETURNING COMMAND WOULD BE:
If you get this, very good, continue with the steps below.
CD\Program Files\Mozilla Firefox
THE RESULT SHOULD BE SOMETHING LIKE THIS:
C:\>CD\Program Files\Mozilla Firefox (Press ENTER)
C:\Program Files\Mozilla Firefox (<<<<< Result)
Now type "firefox".
wait for Firefox to launch now.
it doesn't matter if no internet is available.
Now on firefox, go to File > Open File
Double click "My Computer", and you should see your hard disc there, but don't double click on the hard disc. Instead, click once on the hard disc, RIGHT CLICK, and choose properties. AT THE BOTTOM, UNTICK, I REPEAT, UNTICK THE BOX SAYING "Compress this drive to save space etc....". NOW CLICK APPLY, WAIT, AND I MEAN WAIT PATIENTLY OK? AFTER THAT CLICK ON "OK".
AFTER PRESSING OK, DO A QUICK LOOK AT YOUR DRIVE BY DOUBLE-CLICKING IT NOW. IF ANY FILES/FOLDERS ARE BLUE IN COLOUR INSTEAD OF BLACK, RIGHT-CLICK IT, CHOOSE PROPERTIES, CLICK ADVANCED BUTTON (Beside Read-Only Box and Archive Box), UNTICK, I REPEAT, UNTICK the 3RD BOX Which says "Compress contents to save disc space".
Click OK, Apply and close the folder/file properties.
Now close the box opened by firefox, close firefox, close command prompt AND AT THE BOTTOM RIGHT OF THE FIRST WINDOW WHICH POPS UP MENTIONED EARLIER, PRESS RESTART.
Your computer should be able to start properly now