modifying column type take too much time

Question

  Hello ,
  
     I have 1 table in SQL2005 with 4,00,000 Records . I want to change column type of 1 column from char to varchar. It take too much time & not completes successfully any time .

ALTER TABLE table 1  ALTER COLUMN Comments varchar(5000) null

  I also tried with  other option like
 1)
  Add New Column
  Update data in that column
  Remove old column
  Rename New Column to old column name

 2) By manually changing from Select Table in object Explorer - right click -    modify
 But can not succeed in any way.

Also can not be able to use SQL job agent service due to Express version installed at client.

Is there any way to reduce time in this Query in table with hundreds of record.

Thanks in Advance