What are the real specs of my pc?

Go and get Belarc Advisor, this gives an accurate audit of your system.

Speccy is another nice free system info utility. The difference you may be seeing could be due to an onboard graphics (amd 6540) but the system had a card added (gt440). If you like free ware try FileHippo, they have both free and commercial trials and cover the gambit. You can find speccy and belarc there, just search them in its search window on the top right.

I would use CPU-Z from CPUID.com

As for your specs they are BOTH correct.
It is the Integrated Graphics that is being read, however.
Nvidia GeForce GT440 integrated graphics chipset,

GeForce 400 Series - Wikipedia, the free encyclopedia

Use a better program such as CPU-Z, or Belarc Adviser, (As already stated by Curleyben )

CPUID - System & hardware benchmark, monitoring, reporting

You can also check out the graphics specifications using GPU-Z,

GPU-Z Video card GPU Information Utility

As for which is better?
The dedicated graphics card, AMD HD6540 with 4GB's of graphics ram memory.

Integrated Graphics uses some of the system's resources.
The Processor and Ram Memory.
This slows the computer down, and the graphics process.

A dedicated graphics card has it's own Processor, (G.P.U.
Graphics Processing Unit), and graphics ram memory.
It doesn't need, or needs VERY little, of the system resources.

A dedicated graphics card is always better than Integrated Graphics.

Regards,
joecoolvette

Re-read my previous post. Posting a more in-depth answer;

Processor: List of Intel Core i5 microprocessors - Wikipedia, the free encyclopedia

1024MegaBytes (1024MB) = 1GigaByte (1GB)
Your Ram Memory amount (Memory is 8192MB, or 8GB. (1024MB x 8 = 8192MB)

A look at your motherboard not installed, and has no hardware components on it, (Not advertising for Ebay),

ACER ASPIRE M3910 DESKTOP MOTHERBOARD MB.SDX07.002 MBSDX07002 S1156 H57H-AM2 | eBay

Click on the photo of the motherboard to enlarge.

The alternate Blue and Black long slots, with the white Locking 'ears', are your Ram Memory slots.

Right below the Ram Memory slots is the processor socket. It is an LGA 1155 processor socket. (Socket has the contact pins, processor has the matching socket holes. There are one thousand, one hundred, fifty-five contact pins)

To the right of the processor socket is the PCI-Express x16 expansion slot. Black in color, with a white Locking Arm.

To the upper right of the PCI-Express x16 slot, (By the white Locking Arm), is the Southbridge chip. The Intel Core i processors do not use a Northbridge chip.
(QPI. Quick Point Interconnect ) (Nor do they use a FSB. Front Side Bus)

Processor has Solid Capacitors surrounding it. (Part of the Motherboard Voltage Regulator Circuit. They are probably Polymer solid capacitors. Regarded to be better than Electrolytic Capacitors)

Your computer IS using, (Provided you have your monitor plugged into the graphics card, and Not the motherboard), the AMD Radeon HD6450 graphics card.
(Should have caught that in the previous post. It is an HD6450, not 6540)

Northern Islands (GPU family) - Wikipedia, the free encyclopedia


Regards,
joecoolvette

DXdiag should be the correct one. Your system was set up with a either or video system. Yours seems to have the nvidia in it. Not ATI.

Acer Support: Specifications

Acer Support Specifications stated for Graphics:

"Intel® HD Graphics
Discrete card support for high-end NVIDIA® GeForce® and ATI Radeon™ graphic cards
Microsoft® DirectX® 11 support"

1) Intel HD graphics:

Means IF, the computer doesn't have a graphics card installed, it will be using one of Intel's series of HD Integrated graphics,

Intel HD Graphics - Wikipedia, the free encyclopedia


2) Discrete card support for high-end Nvidia GeForce graphics cards;

Means it can support high-end Nvidia GeForce series of graphics cards.

Comparison of Nvidia graphics processing units - Wikipedia, the free encyclopedia

2a) Discrete card support for high-end ATI Radeon graphics cards;

Means it can support high-end (HD) ATI Radeon graphics cards.

Comparison of AMD graphics processing units - Wikipedia, the free encyclopedia


The statements made in 2) and 2a) hold true, because;

A) The motherboard chipset that is used;

Intel H67 Express chipset,

List of Intel chipsets - Wikipedia, the free encyclopedia

An Intel Core I series compatible chipset.

Looking at the left column drop down to H67.
Now look across the chart, and under the heading - PCI Express Lanes.

PCI-Express 2.0 technology is used. (8 Lanes also )

Doesn't MATTER what GPU (Graphics Processing Unit) is used.

Nvidia GeForce series or AMD ATI Radeon series.

Regards,
joecoolvette