Once you get 7.8 installed, open the window where you have the report you want to convert. Then do these steps:
* right click on the report and choose the top menu item, 'convert'
* accept all the dialogs (changing the name if you want). A new report will appear in the window, offset by about 10 pixels. Keep your old report until you are happy with the new one.
* In the project browser, open the Report folder and then double click on your new report.
* In the data tab, create new data sources that match the old bindings on your old report. This isn't required, but you won't be able to use any of the new functionality until you do, and that's probably why you're converting.
* Check your report in the preview tab. There may be some tweaking to do with your data sources and keys.
There's a few steps here, but it's a one-time process for each report. The layout is saved intact, and that's usually the time consuming part of making reports. We didn't transfer over the data bindings because the new data sources give you a LOT more power and flexibility, and most people will want to rethink their data sources when they convert.