Dance in Second Life is no different from any other entity.
We humans are always trying to find ways to make things faster better and or unique. In doing so the demands get higher.
This applies to dance in sl.
The PC you bought 4 years ago might have been the top of the line at the time, but i can guaranty you its at the bottom of the line now. https://secondlife.com/my/support/system-requirements/
Looking at the recommended requirements i am to think those are the minimum requirements for today's Second Life.
There are 4 main things that directly effect the way your PC operates in Second Life, 3 of them are hardware components in the PC .Memory(RAM) Graphics Card (GPU) and Processor(CPU) , the 4th is your internet connection
Using WIFI .(wireless routers) i read are not good for SL,why? idk.. i dont use them.
Having a good isp(internet service provider) can make or break your SL experience.
The cheapest upgrades to your PC are (in order)
2:GPU (150$ and up)
3:CPU(100$ and up motherboards the same 100$ and up)
CPU is as much or cheaper then GPUs but will most likely require a new motherboard.