Please use the following query:
Select Top 1000000 tblComputers.Computername, tblComputers.ComputerUnique,
tblComputers.Domain, tblDiskdrives.Caption, tblDiskdrives.Description,
tblDiskdrives.DriveType, tblDiskdrives.FileSystem, tblDiskdrives.Freespace,
tblDiskdrives.Size, tblDiskdrives.Volumename,
tblDiskdrives.Volumeserialnumber, tblDiskdrives.Lastchanged
From tblComputers Inner Join
tblDiskdrives On tblComputers.Computername = tblDiskdrives.Computername
Where tblDiskdrives.Caption <> 'A:' And tblDiskdrives.DriveType = 2