Turn off Uneeded Devices
Go to device manager, disable any drivers you do not use or need. For example, firewire or terminal server device redirector.

Turn off Uneeded Services
Go to services. Disable or set to manual all the Windows Services you do not use.

Startup Programs
Go to run, type msconfig. Turn off Programs which arnt needed during bootup. For example; itunes helper, yahoo pager, adobe updater, quicktime etc. Note: Enabling multi processor, in boot, advanced settings does not boost startup time, this is clarified in an article microsoft posted.

Ready Boost
Ready boost can help computers the most with lower amount of ram and a slower hardrive. Use at least a 4gb memory stick.
Ready Boost may cause excessive wear on your usb drive.

Improve your hardrive.
Install a faster hard drive or set up Raid 0 array, with two hard drives. SSD hard drives are more expensive but save money in the long run with lower power consumption. There are many different way to configure your hardrives to best suit your needs. Onboard raid might better then a raid controller, because raid controllers may need time to load during boot up.

Defragment
Start. Programs. Accessories. System Tools. Disk Defragmenter.

Disk Cleanup
Start. Programs. Accessories. System Tools. Disk Cleanup.Remove uneeded data, or reduce data not needed often.

Unistall Uneeded Programs
Go to Control Panel. Programs and features. A hardrive with more space is also a faster hardrive. There are also some extra windows programs which are not needed.

Adjust Performance Settings.
Control Panel. System. Advanced System Settings. Advanced. Performance. Settings. Visual Effects. Adjust to your liking.

Im not going to list every service which can disabled, because it is relative to your needs. Just google it.

There are a few minor other tweaks that can be done. Please post them if you know of them.

Hope this helps,
SineSurfer

Thanks! This was helpful.

This is the long version of Maintenance- something everyone should do but something few bother with!

I would add in how ReadyBoost kinda murders your drive, and it's not as fast as RAM. Extra RAM will last longer and work faster, not only that, but will not cost much more than a good 4GB flash drive (which will die sooner than the RAM).

Ready boost isn't the same thing as pagefile, so windows may not wear it out as fast as one might think. Also new drives are warrenteed and have better longevity then old ones.

If anyone has any data or links on how fast ready boost kills your drive I'd appreciate it.

I'll put a warning note under the ready boost caption.

i'd also add:
Stop Windows from looking for Network files and printers on startup
XP: in Explorer click Tools->Folder Options->View
Vista: Control Panel->Folder Options->View
Then uncheck Automatically search for network folders and printers


Performance Settings / Virtual Memory
(For both boot and run-time performance)
Allocate all the space you need for your pagefile once upfront. Then defrag your pagefile. (One should note this is not the same as normal Windows defrag) (Best to set pagefile min=max upfront so Windows doesn't fragment your pagefile as it grows)

• Determine your max pagefile space based on your current memory (then you needn't change it again unless you change your memory)
• Cleanup/delete files (i.e. create as much disk space as you can)
• Set your pagefile min=max = amount of space you decide you need. Then reboot
• Do a normal Windows defrag (to try and create lots as much adjacent free space as you can)
• Run Pagedefrag to defrag your pagefile (and maybe get it into one or as few as possible contiguous blocks)