These, I can assure you work very very well...
Disable Paging Executive
This will prevent page sections from RAM going to the hard drive. If you have a large amount of RAM at least 1024mb improve your performance considerably due to reduced amount of hard drive swappage. The entry that you will want to modify is called DisablePagingExecutive. Changing this from 0 to 1 will keep the data in your RAM. and off your drive. "DisablePagingExecutive"=dword:00000001
System Cache Boost
The XP kernel can be loaded into your RAM with a simple registry edit. This can greatly improve performance since the NT Kernel will always be in your RAM. With this edit you will allocate roughly 4Mb of your RAM for the kernel. Sometimes more RAM is used but most of the time it is only 4Mb. The entry that you will need to find is called LargeSystemCache and you'll need to change this from 0 to 1 in order to enable this."LargeSystemCache"=dword:00000001
To put both of these RAM tweaks into use you'll add this to your reg file.
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management]
"DisablePagingExecutive"=dword:00000001
"LargeSystemCache"=dword:00000001
I just relised I hadent re_applied this one after fresh install "LargeSystemCache" Programs are now loading twice as fast as they just were.
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Turn off indexing
1. Browse to your hard drive either through Windows Explorer or through my computer
2. Right click your hard drive icon and select properties.
3. At the bottom of this window you'll see "Allow indexing service to index this disk for faster searches," turn this feature off for all of your drives by unchecking the box and clicking ok..
4. After that a window will appear and you'll want to choose apply to all folders and subfolders if you want the full benefit. You could turn this on for selective folders that you search frequently. For the most part you want this off for all of your folders.
Another very good tweek.
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This is the link where these are from, I do not apply all there suggested tweeks but pick & choose as I see fit
http://www.neoseeker.com/Articles/Hardware/Guides/winxptweak/
Beware if your not comfortable tweeking .reg just forget about it.