The Windows operating system allows you to compress the files on your drive to conserve disk space. In some situations, this compression process will compress files required for the operating system to boot. Files that are compressed must be decompressed prior to execution. Since the operating system has not loaded, boot files cannot yet be decompressed. In this case, the operating system will fail to load and a "BootMgr is compressed" message will appear. An easy way around this problem is to boot from the Windows DVD, and use the provided interface to access your drive properties and decompress it.
Turn on the computer, and insert your Windows DVD. Press a random key on your keyboard once you see the "Press any key..." message. This interrupts booting from the hard drive and forces a boot from the Windows DVD. Click the "Next" button at the bottom of the Windows 7 dialog, and then click the "Repair your Computer" link Below. http://windows.microsoft.com/en-US/windows7/What-are-the-system-recovery-options-in-Windows-7 http://msdn.microsoft.com/en-us/library/aa364219(v=vs.85).aspx
File Compression and Decompression Select the "Load Drivers" button at the bottom of the "System Recovery Options" dialog, and click the "OK" button on the "Add Drivers" dialog. This opens a file browser on your screen. Click the "Computer" icon, which is located on the left hand side of the screen. This displays an icon for your disk drive. Right-click your hard drive, and click "Properties. " This opens a Local Disk Properties dialog. Click to deselect the "Compress this drive..." option at the bottom, and then click the "Apply" button. Select the "X" icon to close the file browser window. This takes you back to the Install Windows dialog. Press the "X" icon at the corner of the Install Windows dialog. This opens a cancellation dialog. Select the "Yes" button on this dialog to restart your computer. Hope this helps