i'm using a seagate SATA 500GB for my main drive, with both games and OS on the disk, but in separate partitions. i had, for a month, a western digital raptor -- 10,000 RPM, but i took it back because of its reputation for breaking, and i find that there is not that much difference -- maybe 2 seconds -- in loading with the slower 7200RPM seagate.
for Trainz, the video card seems to be the bottleneck, after you've got a decent enough CPU -- and, i've had several video cards and the current ATI 4890 runs trainz best, with high frame rates and no staggering at all.
for strategy games, like Medieval Total War 2, the faster the CPU the better, since there are non-graphic based computations to compute. but, for sims -- train or flight -- our graphics cards do the more important to them visual object calculations, as the cards themselves are 'computers' designed for that one activity -- the way the add on 'math processor' used to be necessary in the old 286 days to do calculations and graph making.
one thing though -- i'm using GL setting and when i switch to DX i'm getting a lot of stuttering -- i'm Win XP pro, with DX9c -- and, i believe vista guys have DX10? and i don't know if that's a better iteration of DX, though i suppose that trainz doesn't support DX10 itself? But, the GL settings are great and the trainz run on time -- no staggering and laying about at the stations.
in any case, the solid state drives are still experimental and perhaps are losing data and ability over time? and, if you need, you can test something out -- which is to use a 'ram disk' in RAM memory and load Trainz in the RAM disk and see if reading speeds up your trainz experience -- you'd still have to save to hard disk to keep your save, but saving doesn't happen that often for me in Trainz. personally, i've found the RAM disk to be more not worth the trouble with no speed or loading miracles. i still think it's your motherboard and your overclock being out of sync, and that no new and faster harddrive is necessary... or, so it's suggested in the overclocking newsgroups.
mike
I don't have any recommendations yet for SSDs because the brands are still settling down. When they've finally come to a point like the DVD drives and other items with particular manufacturers, then I can recommend the dirves.
Even though you over 1 TB of storage, and I have 2TB spread over 2 drives with No RAID, Trainz likes to dump everything on a single drive. Right now the capacity of the SSD drives available for commercial use are still quite small, and with the way that Trainz likes to fill them up, you might run out of space quickly. These drives will look just like an SATA drive to your system. In fact from what I've read, they use the SATA controller as the interface.
I saw an online demo of some SATA drives in action. The system was unbelievably fast. Thy set them up in a huge RAID. It was done as an experiment and was sponsord by Samsung.
http://www.tomshardware.com/news/samsung-ssd-hdd-raid,7224.html
http://www.youtube.com/watch?v=96dWOEa4Djs
When they are priced reasonably, which I think will happen soon and the brands have settled down, I too will be one of the first to upgrade to them.
John