Video card problem on Acer Aspire 5740g?

hello .. I have an Acer Aspire 5740g and the video card is 512 MB ATI Mobility Radeon 5740g but bios says the card is 2048 or something. How could I do to change and I set my video card 512 MB or less / more.|||try going to sart menu then right click on my computer/computer then left click on properties then device manager look for yellow ? mark right click on that then click uninstall then reboot computer that will reinstall drivers and what you may need|||http://www.techpowerup.com/gpuz/

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