Dual Booting, MBR and Grub

I had Linux and Solaris installed and had an empty partition I wanted to install Windows on. When installing Windows, I was able to choose the correct partition and format it, however then it something about Windows needing the active partition to be set. This is a dos term and meaning is bootable partition. Windows apparently overwrites the Master Boot Record (which is

master boot record (MBR), or partition sector, is the 512-byte boot sector that is the first sector ("LBA Sector 0") of a partitioned data storage device such as a hard disk.

There can however be a boot sector for each partition.

BIOS executes code in the MBR which could be the code that bootstraps windows (called a chain loader ) or it can be code that can load and run Grub, which can bootstrap any OS. Info on how Grub works:

http://www.redhat.com/docs/manuals/linux/RHL-7.2-Manual/ref-guide/ch-grub.html