I'm thinking the 'Pentium 4' was a typo, but if not that could be one of the reasons for lower fps. Also, you might still want to run pingplotter, as it doesn't take long and will at least rule out any network related issues.
You should also check your GPU/CPU temps (try Speedfan at
www.speedfan.org) to make sure they're not too high (which could degrade performance). You're already using Legions Lite (Which, tbh, I wouldn't think a system likes yours would need to use). Other than general maintenance stuff (defrag, antivirus, removing unnecessary background applications), not sure what else I could suggest.