First off, unless you are running one of the older Windows OS's (98, 98se, ect) you might as well ignore this post.
Over at WW2OL, when our game went live on 6/6/2001 it had tons of problems. A great many of those problems were game related, but a significant number were also related to poorly set up computers. WW2OL takes real good computer, well configured and running right because it is a very CPU (processor) dependant and every extra CPU cycle you can get helps a little.
Second Life is very similar to WW2OL in the things it demands from a computer.
During WW2OL's painful first steps, I found myself on the forums a lot helping people get the game running. I also found myself typing the same things over and over for each person...because there are a few very common problems a lot of computer users have. After a few thousand posts typing out the same thing, it occured to me that I have a website and could post all that stuff there and save myself a lot of typing. So...thats what I did.
I created World War Two Online Troublesooting Tips to help players get the game running and running good. These tips can help you even if SL is working okay for you.
This is an old site and I have since retired from tech support and no longer keep it updated. But the info there is still perfectly valid for Win98 based systems. The site is set up in a roughly step by step manner, with simple instructions for things you can do to improve your computer's performance.
Along the left side of the site are the menus. If you go thru these one at a time, in order from top to bottom, the pages will guide you thru a bunch of different things you can try. You dont have to do all of them...and some of them probably wont improve the performance of this game much...such as the HDD tuning tips and virtual memory settings. These tips and tricks are very common and found on many tweaking websites around the net. Virtually all of them are very safe...if the tip causes a problem, its a simple matter to undo it.
I dont know how many of you folks are still running Win98 (I am) and the tips are only really good for Win98. If you are, and are having problems with framerate (FPS, frames per second) in the game...the site might be worth checking out.
Good luck

Avondell