I would like to start off by saying that I have looked around for everything on how to turn XP into Vista. We are not actually doing that; we are simply making it look like Vista. I have searched around and found out what works and what does not. I also know what is safe and what works the best. Since I have tried everything, I will include all of the good ones, but I will recommend the best.
Themes
For the “base” of it, which will do a lot of the work, I used The Vista Transformation Pack 7.0. It works great! It includes: Windows Vista Aero Theme, Windows Vista Basic Theme, Visual Task Tip, ViOrb, Thoosje's Vista Sidebar, and LClock. Too look it's best, I recommend using all of these features, but you do not have to. To get the Vista Transformation Pack 7.0, go here.

Vista Transformation Pack 7.0
Aero Glass Interface
For the best Windows Vista Interface, you need to pay money. You must buy WindowBlinds 5 or 6 to get it. Sorry, but it does not work with the free trial! Although, there are some free programs that will let you do it, but unfortunately they are not as great looking. These include the following - TrueTransparency (I recommend), FastAero, and VystalVivid. Trust me, TrueTransparency is by far the best one that I know. FastAero is pretty good, but the Aero Buttons are not realistic and too large. VystalVivid is probably the best, but it is incredibly annoying because it has this very stupid affect where when you close out of an application, it slowly fades away. Now don't say “Well I think I'll get Vystal then!” because you think you can live with it. TrueTransparency is the best because it looks good except for the text. The text isn't really that bad, it just doesn't look exactly like Vista. To get WindowBlinds, go here. To get TrueTransparency, go here. To get FastAero, go here. And to get VystalVivid, go here.

True Transparency
Windows Flip 3D Feature
The only one that I have tried and liked is WinFlip. WinFlip completely does its job as good as Vista does. All you have to do is download it, run it, then press Windows Key+Tab and there you go! You can download it here.

WinFlip
More Stuff
To get the greatest effect, you should do a couple of things. First, make sure after you've installed everything and set up everything, you should restart again. I found that this sets everything right and gets you more comfortable knowing everything works. Second, you might want to consider downloading everything updated. Make sure that you have Windows Media Player 11, Internet Explorer 8, Firefox 2.0.0.9, XP Service Pack 2, etc. The quickest way to update all Windows Applications is to Run Windows Update. Third, if you have Firefox, listen up because you won't want to miss this! I found an awesome way to make Firefox look exactly like Internet Explorer 7, but it isn't! The best way to do this is to follow this guide.
Enjoy!