Error message download

Are you trying to download a specific Acrobat update?  If so which one?  Could you also please provide the error message?  Also what version of Windows are you using?

to close adobe 8 whihc is not open

It is. Task Manager --> Processes tab --> acrotray.exe. Terminate the process.

is there an update in my existing adobe 8? If so how do i start it?

You're two versions out of date. You did get that warning and upgrade requirement for a reason in teh first place....

Mylenium

Uninstall the existing adobe reader 8 and then download and install Adobe Reader X from the below link.

http://www.adobe.com/products/reader.html