Question SQL Server column data type

[tqmd1]

Dear SIR,
I am using sqlserver2005.
Table1 has a column named bill_no and its type is text
Now I want to change its type "Numeric"
When I do this the it displays this error message

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Microsoft SQL Server Management Studio
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Conversion from 'text' to 'numeric' is not supported on the connected database server.

How to change type text to numeric
I do not want it through vb.net codes.
I want to apply it directly in sqlserver 2005.

Please help