What do you mean "NoLimits.com" doesn't help? Make sure you go to
http://www.nolimitscoaster.com/, go to downloads and select "Update (full version only)" for Windows or Mac.
I've had NL for 3 years now and when I purchased it (in 2007) at the full $29.95 price, they sent me the latest version 1.71. How do you have only 1.55? Seems a bit strange. Especially if you had 1.55, reinstalled it, how would it change to 1.262?
Easiest solution would be a repurchase. I run a ATI Radeon X1900 with under a Gig of Memory. Yes, I can only use 600x800 resolution, but it works fine for my dinosaur PC.