value is a reserved keyword in SQL so you cannot use as is, try the following:
Select ID, Value1, Value2, (Value1+Value2) as [Value] from table where (Value1+Value2)> 100
to see list of reserved keywords, see the following MSDN article:
http://msdn.microsoft.com/en-us/library/aa238507(v=sql.80).aspx[
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