Unfortunately, you cannot make W7 bootable directly because you have installed it in a logical drive and only primary partitions can be "active" (and therefore bootable).
Since you only have 4 partitions, there is no need to have W7 logical. You could reinstall it in a primary partition and then use EasyBCD > BCD Backup/Repair > Change Boot Drive to make it the partition controlling the boot.
If you don't want to reinstall, you'll need to make one of the other primaries the new boot drive (you could give your recovery partition a letter and use that to boot) before you can remove Vista.
Can't do that CG - C is logical.
@panounet - what will you do with the Vista space ?
If you just want it to store user data, you can just delete everything in the vista partition except the \boot folder and bootmgr and the system will carry on booting without you needing to do anything else.
OK. Just set folder options like this, so you can find the boot files, then delete everything on the Vista partition (from W7) except the \boot folder and the file "bootmgr". You can use the D partition space for your W7 files.
If that's so Pat.. , then you can't do it with Windows.
To merge a logical partition with a primary is not possible without using a bootable 3rd party partition manager which can convert the logical into a primary, then do the merge.
Also moving the start position of a partition changes its UID, and hence the BCD will be unable to boot it until you repair the BCD http://neosmart.net/wiki/display/EBCD/Recovering+the+Vista+Bootloader+from+the+DVD
Tell us what you intend to do and we'll advise whether it will work OK.
In that case, I'd advise you to reinstall W7 from scratch, using the "custom" option at the start to reformat and reuse the space taken by the previous Vista and W7 partitions as one large primary.
What you are trying to do in converting W7 to a primary, merging it with another partition and destroying the integrity of the BCD by moving the start point, is not something to contemplate if you are not a confident and experienced user.
You will certainly need to acquire a W7-compatible Partition Manager, and to create a W7 repair disc (Control Panel > Backup > Create System repair disc) before you start.