Seems like you are getting fairly similar queries and responses on the other forum.
I think the immediate answer to your question on here is that the entry in Task Manager for the "system process" is nothing to worry about.
The trojan could easily account for some of your problems and maybe some part of your 1440M of RAM usage, which is quite high. This view seems to be shared by the other forum. Off the top of my head, "from boot up" I would be concerned if the RAM usage logged was as high as 1000M, unless you have one heck of a lot starting up.
If your system is now clear of Trojans/Viruses then it will probably behave itself. Other than that, it is a case of pruning out background programs to see if that reduces RAM usage. Not much more I can add without duplicating what you are getting elsewhere.
No problems posting your query around so long as you let everyone know the final outcome - forums like to know how folk got on.
What's the time?