I am Ricahard john using ACER laptop with windows vista home basic from last december, one month before I had some problem in my system, i couldn't rectify so I reinstalled the system with the CD (Windows anytime upgrade) provided by ACER along with my laptop when I bought. since then the system is asking the product key, my product key is NO LONGER AVAILABLE ( It is the stiker from the back side of the system), but it is not accept the command is comming like invalid key. I couldn't understand what is the problem. Now the windows stopped working. pls let me solve the problem.