Don't forget there are drivers and controllers between the OS and SSD, which can prevent a TRIM command from reaching the SSD.
TRIM commands are sent by Win 7 by default. (0). If a TRIM command gets to a TRIM enabled SSD it will execute the command by default. Exactly when the TRIM command is executed by the SSD is down to the SSD.
With a TRIM enabled OS & SSD "all" you need to do is make sure your controller can pass the command.
The default Win 7 MSAHCI driver enables TRIM pass through as do the Intel RST drivers.
If you use any form of a raid array however TRIM will not be passed to the SSD, unless the SSD is a non member of raid array. (There is some evidence that a pure software raid can pass TRIM, but no concrete prove).
Intel were going to provide a matrix that helped people understand if a system configuration could pass a TRIM command, but they never got around to it.
Shame, because the question is asked over and over again.
