When PC's are slowing down, first run a good utility to clean the system.

Advanced System Care free from iobit. free
Glary Utilities free
Winutilities, free
All offer one click solutions that are very good to optimise a system.
Please do not use Norton as anti virus.

Render settings?

Cast shadows ON
Raytracing ON
Raytrace bounces 2-3
Indirect Light ON
Irradiance caching 0 - 30
Indirect Light Quality 7
Pixel samples 3-5
Min shading rate 0.5
Bucket size 32
Smooth Plygons As required
Use displacement maps => If you use a displacement map somewhere
Poset filter size 3
Post filter type sinc

With little RAM you can set Render in a separate Process in the General preferences.

Oh almost forgot. Windows 7?
Buy a fast 4GB SD card if you have a SD card slot and use the Windows 7 Readyboost option to speed up your machine.
If no SD card slot, you can do the same with a fast 4GB USB stick.

The SD card or stick can be bigger then 4GB, but Readyboost has a max of 4GB.

Euh, Readyboost can handle up to 4 devices of 4GB , so a combination of a SD card and USB sticks works too.

Happy Posering
Tony

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!