Multi Currency

I am trying to set up multi currency functionality. I do follow the instructions

  1. In the Home window, on the Setup menu, choose Settings.
  2. On the left side of the window, click Company and then Currency.
  3. In the Home Currency section, enter the settings for your home currency.
  4. Select the Allow Transactions in a Foreign Currency option.
  5. Select an expense account to Track Exchange and Rounding Differences.
  6. Click OK.

When I get to step 4, I noticed the "Allow Transactions in a Foreign Currency" button is greyed out, so I am not able to select it.

Does anyone know how to solve this problem? BTW, I am using Sage Simply Accounting Premium 2011

Thanks in advance