I have a rather complicated problem with a probably simple solution. I used to have a tri-boot machine - my first primary partition was WinXP Pro, second was a Xubuntu installation with swap on an extended partition, and finally a Windows 7 Pro primary partition.
I deleted WinXP Pro and Xubuntu to create my very first Gentoo Linux installation. While that went well, I accidentally broke my Windows 7 startup. It's listed just fine under LILO (unless I listed it improperly) but Windows 7's BOOTMGR is now missing. I'm assuming the BOOTMGR might have been part of the WinXP installation.
I went to this guide: Bootmgr is missing - Fix
However, I don't want to replace the MBR and break LILO/Gentoo. I just want to reinstall the BOOTMGR onto the Windows 7 Pro partition so I can boot both Gentoo and Windows 7 properly. Of course, I might be misinterpreting where the BOOTMGR is normally located.