You realise that sdb2 is a container for sdb5,6,7?
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 12865 103338081 7 HPFS/NTFS
/dev/sdb2 12866 30401 140857888+ f W95 Ext'd (LBA)
/dev/sdb5 18719 26959 66195603+ 7 HPFS/NTFS
/dev/sdb6 12866 18718 47014159+ 83 Linux
/dev/sdb7 26960 27221 2104483+ 82 Linux swap / Solaris
And you don't have a separate /home do you.
It is possible. Delete sda5 and sda7, resize sda6 and create a new swap at the end.
You know in fact sda6 is the first partition inside the extended sda2 do you.
So I'm not too sure how the device map will look after this and you may have to edit the fstab and menu.lst files.
Does that make sense ?