Do you know what version of Crystal the original report was designed in? Do you know what kind of data connection it's using?
Normally all you have to do is open the report in Crystal XI and save it. Crystal will ask you if you want to upgrade to the latest version.
However, I've run into a few issues with reports that use an OLE DB connection running in Crystal but not running from a program or a website. In those cases, I've had to recreate the report from scratch in XI - which is not as difficult as it sounds because once you have the tables, links, and groups set up, you can copy and paste from the original report to the new one. For formulas and parameters that are used but don't actually appear on the report, pull the object onto the original report, cut, paste into the new report, and delete the object from the report. The formula or parameter will now be available in the new report.
-Dell