1.
first you should open desktop and press "Windows button+R"
2.
in the Run just type the letters "msconfig" with out quotes then click ok
3.
then system configuration window will be opened. in that window select boot tab . it shows os list in your pc select os and click delete option.
4.
click apply and restart the pc.
5.
go to deleted os disk (ex:c:\) select windows folder change folder options with full rights . right click on folder select properties.in that select security tab and select full control.
6.
then delete that folder from pc. then you have sucessfully deleted extra os form pc.
"any problem just put comment"