how about this new code...........
;Gosub ChkInstaller
;Gosub MSIparam

If Not Exist ("C:\Program Files\Adobe 8.0")
MessageBox("Installing Adobe Reader 8.0","ESI International",,2)
Shell '%systemroot%\system32\msiexec.exe /qb!- /i"\\william\admin\users\adobereader\8\AdobeReader 8.0.msi"'
WriteValue ("HKEY_LOCAL_MACHINE\SOFTWARE\Adobe\Acrobat Reader\8.0\AdobeViewer\", "EULA", "1", "REG_DWord")

;--------------------------------------------------------------------------------------------------------------

:UNINSTAR6
; Purpose: To uninstall AdobeReader 6.x
Dim $uninst,$leftpart,$rightpart
; Read Registry key to determine in AR 6 is installed
$uninst=ReadValue("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Adobe Acrobat 6.0","UninstallString")
If $uninst<>""
If Exist ("C:\Program Files\Adobe\Acrobat 6.0\Acrobat\Acrobat.exe")
;Acrobat 6 detected, uninstall. Parse string, add '-y' For quiet mode
$leftpart=Left($uninst,InStr($uninst,"-f")-2)
$rightpart=Right($uninst,Len($uninst)-InStr($uninst,"-f")+1)
$uninst=$leftpart+" -y -a -x "+$rightpart
Shell $uninst

;==============================================================================

:UNINSTAR7
; Purpose: To uninstall AdobeReader 7.x
Dim $uninst,$leftpart,$rightpart
; Read Registry key to determine in AR 7 is installed
$uninst=ReadValue("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Adobe Acrobat 7.0","UninstallString")
If $uninst<>""
If Exist ("C:\Program Files\Adobe\Acrobat 7.0\Acrobat\Acrobat.exe") Exit
; Acrobat 7 detected, uninstall. Parse string, add '-y' for quiet mode
$leftpart=Left($uninst,InStr($uninst,"-f")-2)
$rightpart=Right($uninst,Len($uninst)-InStr($uninst,"-f")+1)
$uninst=$leftpart+" -y -a -x "+$rightpart
Shell $uninst

EndIf