Should I upgrade the internal parts of my current computer? Or should I just buy a new one.?

[Parker]

The computer I'm using is a HP Pavilion a6457c.

I am strictly a Windows user, I know a good amount about Computers, but I'm unsure if I should keep this one and upgrade the Internal parts of it (Ex. Memory, Processor [If possible] etc.) but here are the specs of my current desktop computer.

SPECS:
OS: Windows Vista (Home Premium)
Processor: AMD Phenom™ 8400 Triple-Core 2.10GHz
Memory(RAM) 4.00GB
System type: 64-bit Operating system
System rating: 3.0
Graphics card: NVIDIA GeForce 6150SE nForce 430
Speakers Realtek High Definition Audio
(All are default)
Those are the specs, but here is the general info of the computer (As far as I know)

The computer has no Virus's, it automatically runs file scans once a week, the web browsing is acceptable, (In my opinion, the web-browsing speed 6.5 out of 10.) I'm a pretty heavy 3D gamer and in MMO's such as World of Warcraft and League of Legends I run between 8-25 FPS (Frames Per Second) depending on my location/map and amount of action/players around me, also I've obtained that FPS from having every graphical setting as low as possible. For you gamers out there, you know when you see these words you want too kill the other player, but the computer is Aprox. 5 years old. Though this computers speed is pretty astounding for it's age.
Also, I have a (HP w2207h) 22-inch widescreen monitor that I'm currently using.

My uses; I use this computer mainly for Gaming, Social media, and music. And it does well in all 3 uses.

So thank-you for reading my long summary of the computer! If you think I should upgrade the internal parts of my current computer, please please please list what I should upgrade. If you think I should buy a new computer, please give me a suggestion of what I should buy perhaps? I have a budget of about $1900.

Thank you!

P.s. If you would like too discuss this with me, email me at Zeus6374@hotmail.com.

[Zarn]

I wouldn't upgrade that computer. It's an old motherboard, and replacing the motherboard would then end up with you replacing RAM, and most of the other components.

I'd start saving for a new computer. Currently, I'd prefer a socket 1155 Ivy Bridge-based computer, perhaps with an i3 or i5, 8+ GB of 1600MHz RAM, a fairly powerful GPU, and a fast SATA drive.