My guess... the Samsung 2243SN has only VGA input (D-sub) so most likely you use a passive DVI->VGA adapter to connect this monitor to your card.
A few contacts in the VGA connector let the monitor send a list of supported resolutions to the video card, and that's how the OS typically shows a list of resolutions there. The passive DVI to VGA adapters simply rearrange the contacts between the DVI and VGA sides without any processing, there's just some wires inside basically making connections between contacts.
If the adapter doesn't connect those pins on the VGA side that are used to transfer the resolutions, or maybe if the DVI side is not inserted quite properly inside the video card (so those pins are not connected) then then the video card may not receive the resolutions and default on some lower resolutions.
Unplug and plug again, try several times, blow some air on the dvi connectors in case there's some dust inside causing bad connection.
if that doesn't solve anything, look up what monitors were detected by Windows... if you see there a Samsung SyncMaster something, make sure it's the same model. If it's not, try manually selecting your monitor or if there isn't any, maybe pick a monitor that you know for sure has 1080p resolution.