Trim aligns the drive with a 1024kb cluster for less garbage and more efficient data storage, this just means that data can be easily rearranged and executed. When you currently boot from your HD your system looks for cluster 63, as does Windows Vista.
This for the present time should be no issue though. I have a Windows Vista install on a Crucial 240GB M500 drive, no Trim but also no reserve. I have not allowed Windows to cache to my SSD. Windows loves to waste disk space in allocating space on a Hard Drive where it can cache data and system tasks to. The only issue here is that is will slow down Windows XP in the Short term, but the quicker you can upgrade to a 8 or 16GB memory setup on a 64 bit rig the better.
On 32 bit systems you are restricted to 4GB memory threshold. Since the P45 limit is 8GB and you SATA is 3GB/s you are on SATA II essentially. I know because I currently have my old rig which is an ASUS P5N32-E SLI chipset Motherboard with an Intel Q6600 with 4GB memory onboard. My one used the Nvidia chipset whereas yours uses the Intel P45 chipset which is Crossfire I believe.
Either way it will be nice for you to experiment with and you can even pick up a cheap SATA II SSD of around 120GB for quite a cheap price or go for the latest SATA 600 and you will have no problems going from one setup to another. Beware though, some newer motherboards may not be compatible with some older SSD drives. OCZ have just gone into receivership, so beware. I have an OCZ 480GB drive I run Windows 7 on which is SATA II and is still 3.5 inches of HD. It still runs on my Z77 chipset Motherboard, yet some have had issues running them on the Z87 chipset motherboards.
Anyway I hope this has been of some help to you.
