Just to expand on haakoo's suggestion, alongside a combination of memory, consistent file and folder naming, I also use XnView MP to visually search .xar thumbnails.

Two features I find really useful are the built-in search which allows you to find files by applying conditions such as date range, size etc, and the fact it can also search through sub-folders recursively.

The results can then be viewed and browsed as thumbnails. From there you can open the folder or file in Windows Explorer or directly in your Xara app.
Click image for larger version.  Name: find.png  Views: 83  Size: 92.5 KB  ID: 134771 Click image for larger version.  Name: find conditions.png  Views: 82  Size: 41.8 KB  ID: 134772

The second great feature is the ability to setup favourite folders so you go straight to a particular folder with a single click.

XnView does also have some other potentially useful organising tools, for example, star ranking, colour coding, categories etc, but I've not personally used them.

You may notice the screenshots are from the Mac version, but Xara thumbnails still display ok when viewing an archive of files on an external drive.