Hi admles,
Have a look at this:
Free Hex Editor Neo - Freeware Binary File Editing Software Utility Download this Tool. It works with Vista and is straight forward to use, although, like many commercial software programs, certain features are not available in the free version. It does not have a calculator, but instead links to the one that is included with Vista, which can be configured to operate in 'Scientific' mode by clicking the relevant option under 'View'.
There is a comprehensive help system available, and there is also a forum where further advice on using this program can be found.