First you will have to determine if the resolution is indeed wrong. Go to Menu -> Control Center -> Monitors. See if the maximum allowable resolution is already chosen in the Resolution box. If so, next check the model of the laptop and look online (google box) what the maximum screen resolution for that laptop is. Perhaps Linux Mint is detecting it wrong.
If the maximum screen resolution is detected wrong:
- If you have an AMD (formerly ATI) or NVidia graphics card in the laptop, next step might be to go to Menu -> Control Center -> Additional Drivers and see if you can install the proprietary drivers for the card instead of the default open-source ones. This may work better (it may in fact also not, YMMV).
- Another option, if you have an Intel or AMD (formerly ATI) graphics card, is to use the tool xrandr to force a screen resolution. Short guide is here: http://forums.linuxmint.com/viewtopic.php?f=49&t=76085#p444558
If the maximum screen resolution is detected correctly, and also set correctly, then something else is wrong...