Hi I'm a student from India/single. I'm on F1 visa since 2008. Right now I'm on OPT doing a job and pay my taxes which get cut from my pay check. Recently I received a letter from my bank stating I need to file a W-8BEN form. Can you tell me why should I filing something like this and that too now.
My taxes are withheld from my pay check and I don't have any other source of income as of now.

Can anyone help me with this.

Ps: I used to file my taxes using hr block using 1040a form.

Non-resident aliens fill out from W8BEN for h bank to indicate that they are not subject to withholding.
That means, if you earn interest in your bank account, the bank will not withhold taxes. Interest is not taxable to non-residnet aliens.
Once you change status to a resident alien/permanent resident you would have to submit a form W9 to replace the W8BEN.
If you filed form 1040A, that was a mistake, as non-resident aliens file 1040NR or 1040NR-EZ.
On F1 you are a non-resident for 5 years and would file a non-resident return and form 8843. You would need to amend your returns for all the years you were non-resident alien but filed form 1040A.

Thank you for your time, one quick question, so the bank wants me to fill the W-8BEN only for the reason to tax or not to on the interest I earn from the bank account.
I don't use that bank account any more - if I close the account would there be any impact.

If you close the account and don't expect any interest to be paid to you, you won't need to submit that form anymore. If you keep the account open, you should submit it.