I just uploaded a completely new version of HPI converter. This version offers no new functionalities .... except for a totally rewritten UI. HPI Converter is now able to display all HPI Images in a thumbnail like view - allowing you to easily find that HPI file you were looking for.
The HPI backend now uses the FreeImage Library instead of GDI+ to convert the images. Although this is not much faster than GDI+ FreeImage provides a much simpler API and more possibilities for following versions of HPI Converter.