The CPU can be upgraded to a quadcore APU .
You need to check the motherboard make and model [ which will be printed on the mb ] and then head for the makers webpage for that board and find a cpu support list
The most likely upgrade , and best value if you are going to add a graphics card is likely to be
AMD 760K Richland 3.8GHz Socket FM2 100W $90
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Its a quadcore , unlocked FM2 APU with the graphics disabled
You should also take the RAM out of the machine and get another identical stick you can add back so you have dual channel RAM
Then you would need to add a graphics card . What you buy depends on 3 things
1/ the make and wattage of your power supply
2/ the resolution of your monitor
3/ your budget
Please let us know .............