ROW_NUMBER() - Start over for every change in value

I havea table like
acct_no    code
1111         1234
1111         2234
2222        33333
3333       88888
3333      77777

And need to through a row_number in - but start it over with each new acct_no - so
acct_no    code   row
1111         1234     1
1111         2234     2
2222        33333    1
3333       88888     1
3333      77777      2
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select *, row = row_number() over (partition by acct_no order by code)
from table1

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Microsoft SQL Server 2005

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