Hmmm, those units can give a fan error too when the fan assembly inside fills up with dust - it can ball up in there. If you remove the keyboard and a shield, you can see the fan assembly to examine it for dust buildup. BTW, you can download the Hardware Maintenance Manual for your unit (the same manual authorized service techs use...) from
Here. It will tell you a ton about your unit's parts, disassembly, error messages, troubleshooting, and more.
So we can help better, can you post the full machine type (such as 2628-au1) and serial number of the unit? You'll find those listed on the bottom of your lappie. Setting the refresh rate varies depending on the video chip installed in the unit and therefore the software used to configure it...
As an example - for an ATI video chip - you should be able to gain access to the video chip control panel software by right clicking on the desktop, selecting Properties, Settings tab. At this point, you should be able to change resolutions (which might help...). Clicking the Advanced tab should give you access to many more settings. One of those in the Advanced settings should be the Adapter tab - where you can "List All Modes" and select a resolution and refresh rate of your choice.