I've been a long time XP user, but I've always liked the old Windows 2000 theme.
Now, XP and up to 7 comes default with Windows Classic theme installed, however there is a way to get all those good old 16-bit W2000 icons for XP without having to manually change them.
I discovered this program a couple of years ago, and it's called Inexperience Patcher.
This modifies your .dll files to contain all the old Windows 2000 icons and enables them, including even the grayed-out-icons-in-your-explorer-bar-that-colors-up-when-you-move-your-cursor-over-them. Yeah.
It also has an active reloader, which means if a Windows update replaces a .dll containing an icon that the Inexperience Patcher wants to use, it reloads that file automatically. It doesn't hog any system resources, rather the opposite.
Check it out, there are screenshots on the DeviantArt page.
Now, XP and up to 7 comes default with Windows Classic theme installed, however there is a way to get all those good old 16-bit W2000 icons for XP without having to manually change them.
I discovered this program a couple of years ago, and it's called Inexperience Patcher.
This modifies your .dll files to contain all the old Windows 2000 icons and enables them, including even the grayed-out-icons-in-your-explorer-bar-that-colors-up-when-you-move-your-cursor-over-them. Yeah.
It also has an active reloader, which means if a Windows update replaces a .dll containing an icon that the Inexperience Patcher wants to use, it reloads that file automatically. It doesn't hog any system resources, rather the opposite.
Check it out, there are screenshots on the DeviantArt page.