RAM vs new hard drive

[Fatcatonrampage]

To buy memory, or a new hard drive?

First off, before i get started, the basics of my PC specs.
This is my "Throw together" PC, and it needs improvement:

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Windows 7 64 bit Ultimate
CPU: AMD A8-3850 @3.6ghz
AMD Radeon HD 7700 Series
MSI A55M-P33 motherboard
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As far as this goes, i have a decent system. now here is where i don't.

Hard Drive:

Storage Capacity: 80 GB
Rotational Speed: 7200 rpm
Maximum External Data Transfer Rate: 150 MBps (1.2 Gbps)
Manufacturer Part Number: 6L080M0

RAM: (that's right, only one)

Memory type DDR3
Manufacturer (ID) Kingston
Size 4096 MB
Max bandwidth PC3-10700 (667 MHz)
Serial number 8A38FD0B
Number of banks 8
Nominal Voltage 1.50 Volts
(side note: my motherboard only has two slots for ram)

I'm cheap, and I don't really want to spend over $100 for one or the other, or both maybe
So... New Hard drive, or memory?
Anything that will help in speed would be fine, or overall improvement.

 

[Rockdpm]

Well you could get a SSD and a higher capacity than your 80GB for the price of a new Hard drive. But since you don't want to spend over 100$ then I would upgrade your ram

 

[Sooth1]

http://www.newegg.com/Product/Product.aspx?Item=N82E16822136769 - 64.99

http://www.newegg.com/Product/Product.aspx?Item=N82E16820231461 - 43.99

Edited - This memory is verified to work with your board.

A little over budget but will be a good upgrade.