Fixed it myself (worked for me anyway):
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[web30ossearch](@comp varchar(300))
AS SELECT dbo.tblComputers.Computername, dbo.tblOperatingsystem.Description, dbo.tblComputers.Domain, dbo.tblOperatingsystem.Caption,
CAST(dbo.web30ProcessorCapacity.NrOfProcessors AS varchar) + ' * ' + CAST(dbo.web30ProcessorCapacity.MaxClockSpeed AS varchar)
+ ' Mhz' AS Processor, CAST(CAST(CAST(dbo.tblComputersystem.TotalPhysicalMemory AS bigint) / 1024 / 1024 AS NUMERIC) AS varchar)
+ ' MB' AS Memory, dbo.tblComputers.Lastseen AS [Last seen], CASE ISNULL(dbo.tblOperatingsystem.Description, 'NOT SCANNED')
WHEN 'NOT SCANNED' THEN 1 ELSE 0 END AS Notscanned
FROM dbo.tblComputers LEFT OUTER JOIN
dbo.tblComputersystem ON dbo.tblComputers.Computername = dbo.tblComputersystem.Computername LEFT OUTER JOIN
dbo.web30ProcessorCapacity ON dbo.tblComputers.Computername = dbo.web30ProcessorCapacity.Computername LEFT OUTER JOIN
dbo.tblComputerSystemProduct ON dbo.tblComputers.Computername = dbo.tblComputerSystemProduct.Computername LEFT OUTER JOIN
dbo.tblOperatingsystem ON dbo.tblComputers.Computername = dbo.tblOperatingsystem.Computername
WHERE (dbo.tblOperatingsystem.Caption = @comp)
ORDER BY dbo.tblComputers.Computername