Warning : Missing AA#

I have a system with Intel core i3 processor , Intel 61WWB3 Motherboard , 4 GB Ddr3 RAM , 1 TB Seagate Harddisk with Windows 8.1 installed in it .

The system was running fairly and recently when i started up the PC ,

• Sometimes it is showing the message

     " The following warnings were detected during this boot
     WARNING : Missing AA# "

     and then it loads Windows.

     But the system is too slow. It gets hang for even a mousescroll .

• Sometimes it shows the message
  "Insert proper booting device or reboot "

I tried to reinstal the OS .

But the system is not booting from the CD.

Also I cant change the booting device Priority .

I have connected a brand new Harddisk. But it shows the same message in the second case.
I have also connected a harddisk installed with Win 7 . It stops before the logon screen  and starts again .

Please help me with my problem