Then replace the Keyboard. http://www.sparepartswarehouse.com/Sony,Vaio,VGN-AR150G,Laptop,Keyboards.aspx
In the above link where it states in bold letters -
Service manuals for Sony VAIO laptops and notebooks,
,left-click on - Get it here - to the right of VGN-AR.
This Service Manual is in PDF file format. The computer you are using now has Adobe Reader on it, which uses PDF files.
After you click on the file name, (VGN-AR), it may take up to 30 seconds, before the first page comes up.
Not your laptop, but perhaps this will give more guidance, in removing and replacing the Keyboard,
Just follow the steps up to removing the Keyboard. These are listed just to give you more info on replacing a Keyboard, not disassembling the entire laptop.
For additional questions please post in a Comment.
[ WOW, that Keyboard is expensive! Suggest you look around for a better deal. I just posted that example to give you info. Average price SHOULD be no more than $40 to $50. Ebay? ]