To use multiple currencies, your administrator must specify which currencies are supported for your organization.
Active currencies—These represent countries in which your organization does business. Only active currencies can be entered in opportunities, forecasts, and other items.Once you activate a currency, you can never permanently delete it.
Inactive currencies—These are currencies that your organization no longer uses. You may have existing records that use inactive currencies, but you cannot enter new amounts in inactive currencies.
To activate new currencies:
Click Your Name | Setup | Company Profile | Manage Currencies.
Click New in the Active Currencies related list.
Select a currency. Currencies are alphabetized using their ISO currency code.
Enter the conversion rate relative to your corporate currency.
Specify the number of decimal places to show for amounts in this currency.
Click Save.
To activate a currency from the list of inactive currencies, click Activate next to the currency.
To deactivate a currency, click Deactivate next to the currency. Deactivating a currency does not alter amounts in items that use that currency. However, you can no longer enter new amounts using the inactive currency.
Cheers!!!