Before you bitch at me, I used to be a hater too, until I realised that Vista has FAR more potential for power, and looks nicer...
Vista is not bad, at all. In fact, I'd go as far to say that Vista is one of the most reliable OS's I've ever used. It never, ever crashes (unless you poke it with a big, RAMHOG-shaped stick), and the potential for customisation is far better than XP. Even if you have the magic 3GB RAM that is required for Vista to run smoothly, you can still use this to further speed up your system. Anyway, Vista is great, IF you know how to handle it well. Here are some pointers as to how to make your Vista rig run reliably and quickly:
1. Get rid of your crap
Yes, it takes time, but dear god, this helps... Every time you see something that you do not use any more, get rid of it. Whenever your hard drive start to fill up, delete some of your crap, or put it on a memory stick or something... You can also use the Disk Cleanup tool to get rid of excess crap. Make sure to get rid of thumbnails.
2. Tweak your appearance
Even if you install a custom theme, you can still turn down some of the SFX, and it'll still look sexy. When you do, click "Effects", and turn off as much as you can.
3. Keep your crap up to date
This is stuff like drivers and updates. Install regularly.
4. Tweaking your registry
Make sure to Google some Vista registry tweaks, these are awesome.
5. Basic maintenance
Keep your system up to speed by doing the following, in this order -
a. Clean up un-used crap
b. Use Disk Cleanup
c. Defragment your system drive
This will keep your system running like a dream. Make sure to re-boot afterwards.
6. Turning off un-neccessary start-up programs and services
This will speed up your boot-times. Click the start orb, and type "msconfig", without quotes. Click the program at the top of the list. When it appears, click the Startup tab. Disable unused programs. Exit without restart. Click the start orb again, then type "services.msc" without quotes. Disable any servies that are un-needed. Doing this dramatocally increases performance.
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OK? This will keep Vista running just as bug-free and just as quick(if not quicker) than XP.
Let me know if this improved your system performance.