PD Tweaker is an Application Enhancer (APE) plugin that addresses a few shortcomings in Parallels Desktop 1.0 for Intel-based Macintoshes.

It has two major features which can be enabled separately:
Optimizes caching for HDD and SAV files: A much better caching strategy for these files is actually no caching at all. Caching large files is actually harmful to your Mac's overall performance. HDD files do not need caching because the client OS will already have a cache layer. SAV files are streamed in and out and don't need to reside in the disk cache.
Always writes HDD and SAV files all the way to disk: Your data is precious. Especially data like a HDD file that took you hours to install and configure.

Requirements:
Parallels Desktop 1.0
Unsanity's Application Enhancer

Intel Required

Limitations:
Project has been abandoned.