What is the PC used for?
A PC that is complete and utter rubbish for, say, gaming, could be perfect for office tasks.
Your PC is OK for web browsing, office tasks, playing old/bad graphics games, and so on.
For anything intensive, it's not great.
It needs graphics and more RAM mainly.
A new CPU may be appropriate for some tasks, but that may necessitate a new motherboard, as may a graphics card.