If your prefetcher is not running than your boot and application startup times are reduced. This is an irrefutable fact. If you think otherwise then you have either not properly tested this or do not understand how Windows Prefetching works.

It is impossible for Prefetching to slow your system down on a properly working system.

Prefetching has nothing to do with Searching. Stop guessing and read how this works. Cleaning the folder does nothing but SLOW DOWN your system. There is absolutely no performance improvement EVER:

MICROSOFT ARTICLES:

Windows XP: Kernel Improvements Create a More Robust, Powerful, and Scalable OS
Windows XP: Kernel Improvements Create a More Robust, Powerful, and Scalable OS -- MSDN Magazine, December 2001

Kernel Enhancements for Windows XP
Kernel Enhancements for Windows XP

Windows XP Performance
Microsoft Windows XP Performance

Benchmarking on Windows XP
Benchmarking on Windows XP: Home Edition and Professional

Windows XP Professional Resource Kit
Windows XP Resource Kit: Troubleshooting Disks and File Systems

http://download.microsoft.com/downlo...%20Windows.doc


EXPERTS:

Ryan Myers - Windows Client Performance Team

Misinformation and the The Prefetch Flag
Funny, It Worked Last Time : Misinformation and the The Prefetch Flag


Ed Bott - Author Widows XP Inside Out

One more time: do not clean out your Prefetch folder!
One more time: do not clean out your Prefetch folder! | Ed Bott’s Windows Expertise |

Beware of Bogus XP Advice
Beware of Bogus XP Advice | Ed Bott’s Windows Expertise |

Tip of the day: Don’t clean out the Prefetch folder
Tip of the day: Don’t clean out the Prefetch folder | Ed Bott’s Windows Expertise |


Mark Russinovich - Author Windows Internals

Microsoft® Windows® Internals, Fourth Edition: Microsoft Windows Server™ 2003, Windows XP, and Windows 2000


As for "Force Windows to unload DLLs" it doesn't do anything in Windows XP.