New to SQL Server

We're running SQL Server 7 with OTG (imaging) software, trying to convert a column size on a table with approximately 28million rows. This process has been running for 135 hours. We feel the culprit making it run so long is transaction logging?, and we need to know if there is any way to dynamically turn it off, truncate it, or anything to improve this performance. It appears to be getting slower as time goes on, as it only inserted 4.5 million rows in a 24 hour period. Help!

You can't disable transaction logging. Other option is to BCP out your table, recreate the table with new column definition, change database recovery model to BULK LOAD, then import data using bcp or BULK INSERT, change the recovery model to full and take a full backup.