All my PC applications turned to .lnk

all my PC applications like Excel Word PS Powerpoint Explorer and even Google Chrome .exe has turned to .lnk and their default program is set to Word...so i click on Google Chrome it opens in Word...due to which i am unable to open them properly. how do i revert this setting back to default...plzzz help...System restore tried..no use...suggest sumthng effective...
for example when i open a saved workbook it opens in Excel properly...but when i click on Microsoft excel icon for a new workbook...it opens in MS Word as it is now a .lnk file.....HELPPPPPPPPPPPPPPPPPPPPPPP!!!!!!!!!!!