Absolutely, If you've purchased Tweet Whistle, you can use it on as many computers as you'd like.

All the historical data in Tweet Whistle is stored in a small lightweight database so moving it from one machine to another is easy. Just follow these steps:

From windows explorer, navigate to the location where you installed Tweet Whistle
(e.g. C:\Program Files\Tweet Whistle )

Copy the accounts.db file to the new location where you've installed Tweet Whistle.

By default this option is turned off. From the Settings menu click the "Turn on Automatic Updates" item. Now every time you start Tweet Whistle it will automatically check for updates and notify you if one is available.

You can also check manually for updates by clicking the "Check for Updates" option under the Help menu.

Tweet Whistle is built using the lastest API from twitter and they only allow clients to make a limited number of calls in a given hour. Rate limiting only applies to Tweet Whistle methods that request information with the HTTP GET command. API methods that use HTTP POST to submit data to Twitter, such as follows, unfollows, messages, and tweets do not affect rate limits.

If you do approach the 150 limit within the hour we please ask that you take a break until the rate limit resets at the end of the hour.

Pay close attention to the statistics screen and the number of New Follws vs Already Following. The Follows Sent counter is a sum of the two below it. If you don't see your following count increase it means that you're trying to follow people that you're already following.

This happens occasionaly on Windows Vista resulting from certain security settings. You can simply right click the TweetWhistle icon file and choose "Run as administrator".