Try this...
Hi,
Go back to "Display Properties" > "Settings" Tab.
Set the "Scren Resolution" slider to "800 by 600 pixels".
Set the "Color Quality" to "Medium (16 Bit)" and then try changing the Refresh Rate.
If you can set the Refresh Rate now, set it to "75 Hertz" or lower. Apply all the changes and Restart.
If you can't change and still see "Default hardware setting" there, Apply the changes above and Close.
Now, open the "Display Properties" again and then try to set the Refresh Rate. If you still can't, Restart.
On Restart, check if you can boot normally. If you can, just boot normally.
If not, boot in "Safe Mode" and try to set the Refersh Rate again.
Once you set "Screen Resolution" to 800x600, "Color Quality" to 16 bit
and "Refresh rate" to 75 Hz or lower, you should be able to boot normally.
Once you do, simply change the settings to the values your system is comfortable with.
Ravi