3 folders that I'm told don't belong on my desktop

[emarell]

I'm running 32-bit Vista with SP1. There's one and only one user - me - and of course I'm the administrator too. Regarding my trio of mysterious folders, another forum's participant told me these three folders are not supposed to appear on my desktop: Local, LocalLow, and Roaming. These are supposed to be, he said, "under a hidden folder called AppData." And he warned me it bodes ill because these folders will grow and grow as I add more software, slowing "your desktop" down.

Just for starters I do not find any folder called exactly AppData. I do find AppData(7) and it seems to be part of the one and only user desktop.

I am supposed to, he says, either figure out how the displacement of the three folders happened or else start over with a reinstall of Vista.

But my ignorance is showing. If only one user (me) ever uses the machine, why are large folders on the desktop going to slow it down? I have the - perhaps naive - idea that a hard drive has so much room on it, and if only I am using it...

Finding the culprit or my own mouse mistake - not a realistic task, given the megabunches of stuff I've done during this machine's first two weeks (files, fonts, browser favorites, etc. xferred over from a Win 98SE machine; older software installed; current versions of numerous programs installed).

My vague instincts point at one of these: a very old version of Photoshop (5.0, specifically) which mostly works OK; a fresh download/install of either Thunderbird 2.0.0.16 or Firefox 3.0.1 (Firefox, twice upon a time in an older version, installed itself in a very bizarre location on my old machine); running [parts of] Office 2000 on this new machine despite the fact that so far it seems perfectly OK. The thing is, were I to reinstall Vista, I'd repeat all these additions!

If possible, I'd rather just put up with the anomalous placement of those three folders - any input?