I think it's due to your monitor drivers 
If you installed your manufacturer's drivers than it should've showed other refresh rates.
If you installed standard drivers from Window's library try Super VGA 1024x768@75 Hz and it should show at least 75, beside optimal and adapter's default
Go to monitor, click on change, click next, "Display a list of the drivers in a specific location....", next, show all hardware (here you select what monitor you want), next and finish.
Could you tell us what monitor you have ?

If you installed your manufacturer's drivers than it should've showed other refresh rates.
If you installed standard drivers from Window's library try Super VGA 1024x768@75 Hz and it should show at least 75, beside optimal and adapter's default

Go to monitor, click on change, click next, "Display a list of the drivers in a specific location....", next, show all hardware (here you select what monitor you want), next and finish.
Could you tell us what monitor you have ?

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