If you are currently running Win7, your installation should be good. You should update to the current Intel Matrix Storage drivers.
Is your chipset hard-drive controller set to IDE legacy mode or AHCI mode? Until Tecmo34 stirred things up recently, the common wisdom was that you need AHCI mode for the TRIM command to be passed. Now this is in question.
Do I need to re install Windows on the Primary drive which is a Momentus XT 500gb for Trim to be activated on the SSD?
My mobo is a ASUS P8H67 micro atx.
1) For the new SSD to use trim, the sata mode of the attachment on which the SSD is installed should be AHCI.
Since AHCI is a subset of raid, raid mode is ok also, if you are using current intel drivers. There is some confusion in that a SSD will not get the trim command, if it is part of a raid array.
2) Your ssd will probably still work well even without trim. Reads will be very fast. Depending on the specific ssd, there will be some slowness while updating, once the whole drive has been filled.
3) Most of the time, a SSD is the better option for the os, and a conventional hard drive for data. In this case, I would try to use the SSD for the OS and the momentus for the storage drive.