UPDATE: After losing important data due to FreeCommander bugs, I can no longer recommend this application. The developer simply does not perform adequate testing before releases, and does not have any dedicated QA testers. This application has great potential, but overall the project needs a much higher level of QC to recommend it universally.
FreeCommander XE will do everything you want.
You wanted:
- Windows 7 or Windows XP compatibility
FreeCommander XE is compatible with both Windows 7 and Windows XP.
It's setup tool works with Windows 7, but not XP. Regardless, you can use the portable version of FreeCommander XE with both Windows 7 and Windows XP.
- Preview jpg, pdf, rtf, doc, docx and epub files (without launching another program)
FreeCommander XE can preview all those document types. An internal PDF viewer was just added to the donation version, and will likely be included with the next free version. Besides the new internal PDF viewer, FreeCommander XE can also take advantage of the native Windows file previewers as well as Total Commander plugins (just like Universal Viewer). For more details, please see this thread on the FreeCommander forums.
I find that FreeCommander is a bit of a "hidden gem" in the world of Windows software. Although it has a substantial user-base, I don't think it's as large as I would expect for such a powerful tool.
Does it have any downsides? Yes:
- It is closed-source written by just 1 developer. This is very unfortunate, as the project would really benefit if it was an open-source project.
- Besides the developer, there is no one assigned to perform QA testing or bug reporting. Because of this, it may have more bugs than open-source programs that have larger communities.
- The developer is not the best communicator on his own forums, so answers to technical questions are not very thorough and responses to bug reports are often lacking.
- Support for OS dark themes still needs quite a bit of work, but it has come a long way. Recently, it took a step backward in this regard, but hopefully the developer will fix things soon.
- It is limited to 2 panes (each with virtually unlimited tabs). It does not have any way to show 3 or more panes.
- The UI is exceptionally flexible and customizable. That said, the developer does not have the greatest sense of aesthetics, so some UI elements could really use refinement.
Overall, I think FreeCommander suits your requirements quite well. It meets your 2 requirements, and provides an excellent array of powerful functionality.
The 32-bit portable and installer releases of FreeCommander are available without charge from:
https://freecommander.com/en/downloads-portable/
The free version gets updated about once per year, which in my opinion, really is not frequent enough if you use it regularly.
If you make a donation, you will have access to more frequent releases as well as the 64-bit version. The requested donations range from €5 for a 1-time download to €32 for lifetime downloads. The option of €11 for 1 year of downloads is also available.
Screenshot:
(source: freecommander.com)