Why you're still using Pentium, or why Windows 7 is even on a Pentium is way beyond me. That's your first problem.
Second, your memory seems to be alright, unless you're running OpenBVE with a ton of other processes, at which point yes, it will lag.
Third, programs like Trainz and OpenBVE do not run well on Intel Integrated Graphics, which is what you have. It means that it's integrated to the motherboard, and that there is no graphics card at all, whereas a computer with an AMD processor and an AMD/Nvidia card would work just fine. This laptop model has reached its limit as far as performance.
BStyles