BOOTMGR is missing after setting new partition active

Have you checked your bios to make sure the drive is selected as first boot (if you have more than one physical drive that is)?

Ok guys, i fixed it, turned out that the command promt just had a huge lag in it. For some reason i couldnt set it back to the windows c drive, it gave me the error again when i rebooted, so i set it to the partition 1 100mb drive, and it fixed it. So im all set. Determination is the key to life, with determination, no matter what you are faced with, you can accomplish anything.

You just dont know how many hours i have been working at this

rwalkerfla said:

Ok guys, i fixed it, turned out that the command promt just had a huge lag in it. For some reason i couldnt set it back to the windows c drive, it gave me the error again when i rebooted, so i set it to the partition 1 100mb drive, and it fixed it. So im all set. Determination is the key to life, with determination, no matter what you are faced with, you can accomplish anything.

rwalkerfla said:

You just dont know how many hours i have been working at this

We all are very glad you got it fixed. And may I say, in the kindest way I know how, you have learned an important lesson today. It is OK to learn by doing, but be prepared to return your system to the way it was before experimenting. That means backups, and a "System Repair" CD.

Please look here on how to make a repair cd for your computer. Repair CD - System Repair Disk

There is an extensive library of tutorials here to help you as well: Windows 7 - Tutorial Index

Good job!
Robert

gregrocker said:

If you cannot access the Repair console by tapping F8 during bootup, then You will need the System Repair CD to use Diskpart commands to mark the Win7 partition active again, then possibly need to run Startup Repair up to 3 times with reboots to repair MBR.

Boot Repair CD, open a Command line and type this to set Win7 active again:

DISKPART
LIST DISK
SELECT DISK # (# for Win7 disk)
LIST PARTITION
SELECT PARTITION # (# for Win7 partition, or 100mb System Reserved partition if you have it)
ACTIVE
EXIT

This may start it, but if not you need to reboot the Repair CD to run Startup Repair up to 3 separate times with reboots to repair or rewrite the MBR.

Thanks gregrocker!

I've just screwed up my computer badly by setting second partition on boot drive as Active. After rebooting I got the dreaded BOOTMGR is missing...

Windows Repair disk didn't do the trick. It went through motions, but after rebooting error was still there. I think what made matters worse is that my second drive (D) was marked as Active. After several unsuccessful attempts and trying various things came across this thread and it saved me! diskpart did the trick!

Good to hear.

Updating with newer resources since 2010:

Mark the 100mb System Reserved (preferred) or C Partition Active
Then run Startup Repair - Run 3 Separate Times
Everything else that can be done is here for Troubleshooting Windows 7 Failure to Start