Hmmm... All those ORs in the ON clauses looks pretty messy. Here's an alternate way but I haven't tested to see if it performs better:

DECLARE @T1 TABLE (comp_name VARCHAR(10))

DECLARE @T2 TABLE (comp_name VARCHAR(10))

DECLARE @T3 TABLE (comp_name VARCHAR(10))

DECLARE @T4 TABLE (comp_name VARCHAR(10))

INSERT INTO @T1

SELECT 'comp1' UNION ALL SELECT 'comp2' UNION ALL SELECT 'comp3'

UNION ALL SELECT 'comp4' UNION ALL SELECT 'comp5' UNION ALL SELECT 'comp6'

INSERT INTO @T2

SELECT 'comp2' UNION ALL SELECT 'comp3' UNION ALL SELECT 'comp4'

UNION ALL SELECT 'comp7' UNION ALL SELECT 'comp8' UNION ALL SELECT 'comp9'

UNION ALL SELECT 'comp10'

INSERT INTO @T3

SELECT 'comp1' UNION ALL SELECT 'comp2' UNION ALL SELECT 'comp3'

UNION ALL SELECT 'comp4' UNION ALL SELECT 'comp6'

INSERT INTO @T4

SELECT 'comp1' UNION ALL SELECT 'comp2' UNION ALL SELECT 'comp3'

UNION ALL SELECT 'comp6'

--Tbl1Tbl2Tbl3Tbl4

--comp1Nullcomp1comp1

--comp2comp2comp2comp2

--comp3comp3comp3comp3

--comp4comp4comp4Null

--comp5NullNullNull

--comp6Nullcomp6comp6

--Nullcomp7NullNull

--Nullcomp8NullNull

--Nullcomp9NullNull

--Nullcomp10NullNull

;WITH AllComputers AS (

SELECT comp_name FROM @T1 UNION

SELECT comp_name FROM @T2 UNION

SELECT comp_name FROM @T3 UNION

SELECT comp_name FROM @T4)

SELECT a.comp_name

,T1=(SELECT comp_name FROM @T1 b WHERE a.comp_name = b.comp_name)

,T2=(SELECT comp_name FROM @T2 b WHERE a.comp_name = b.comp_name)

,T3=(SELECT comp_name FROM @T3 b WHERE a.comp_name = b.comp_name)

,T4=(SELECT comp_name FROM @T4 b WHERE a.comp_name = b.comp_name)

FROM AllComputers a

ORDER BY CAST(STUFF(a.comp_name, 1, 4, '') AS INT)

Almost, kinda, sorta like a CROSSTAB query.