I have been using a dual boot Windows/Ubuntu system since 8.04 and successfully upgraded to 8.10 and 9.04 (Windows is XP sp3).

I now need to encrypt my hard drive but only the windows partition. The software I will be using can cope with this as long as I have the original Windows MBR in place and then add an extra option in the windows boot loader to boot to linux.

My windows partition is ntfs and I have followed the following instructions given in the encryption software guide.

sudo dd if=/dev/sda3 of=/media/linux.tr0 bs=512 count=1 [Enter]
sudo mkdir /media/disk-c [Enter]

sudo mount -t ntfs /dev/sda2 /media/disk-c [Enter]

I then had to boot into Windows and go to the System Control Panel, click the advance tab and in the Startup and Recovery section, click the Settings button. I then clicked the EDIT button to edit the Boot.ini file.

My file had the following

[boot loader]
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOW S
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Micro soft Windows XP
Professional" /noexecute=optin /fastdetect

and I added
to the end and saved

Finally in the Command Prompt window, I typed
attrib +H +S +R BOOT.INI [Enter]
attrib +H +S +R linux.tr0 [Enter]

I then rebooted... GRUB still took over as bootloader and I selected Windows
As Windows began to boot I got the Windows Boot Manager and there I selected Linux.

This took me to GRUB and an error 18
eventually the machine rebooted and I got GRUB as the initial bootloader.

I want to be sure that if I now use fixmbr in Windows I will still be able to boot into Linux without getting the Error 18.

Should I go ahead and use fixmbr or is there something else I need to do. Once the bootloader is windows then I can use the encryption software and encrypt the windows partition only.

Any help appreciated