Lenovo IdeaCentre K450 Desktop - Manual (Page 36)

b. Remove the screw that secures the graphics card latch to the chassis, open it, and remove
the Duo-graphics cards connector.
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c. Remove the graphics card by pulling it straight out of the connector.
If your computer has a single graphics card installed, follow the steps below to replace it:
30 IdeaCentre K4 SeriesHardware Maintenance Manual