Here's a quick report that will show you a list of PCs that do not have a particular piece of software installed on them. Simply replace '%Adobe Flash Player %' with whatever software you are looking for.
Select Distinct Top 1000000 tblComputers.Computername, tblComputers.ComputerUnique From tblSoftware soft Inner Join tblComputers On soft.ComputerName = tblComputers.Computername Where (Select Count(*) From tblSoftware Where tblSoftware.softwareName Like '%Adobe Flash Player %' And tblSoftware.ComputerName = soft.ComputerName) < 1
If you are looking for something like Adobe Reader/Acrobat and need to check for multiple entries, the following can be used as well:
Select Distinct Top 1000000 tblComputers.Computername, tblComputers.ComputerUnique From tblSoftware soft Inner Join tblComputers On soft.ComputerName = tblComputers.Computername Where (Select Count(*) From tblSoftware Where (tblSoftware.softwareName Like '%Adobe Acrobat%' Or tblSoftware.softwareName Like '%Adobe Reader%') And tblSoftware.ComputerName = soft.ComputerName) < 1