That's irrelevant.
It doesn't matter if your computer detects your keyboard and mouse during the POST screen (the black startup screen that detects your RAM, hard drives, and all that good stuff).
Windows doesn't care.
Let's say you have six USB ports. To make this easier, we'll label them 1, 2, 3, 4, 5, and 6.
Let's say you had your keyboard plugged in USB port 1.
Let's say you had your mouse plugged in USB port 2.
Let's say that your family member decided to move your keyboard to USB port 3 and the mouse to USB port 4 because he/she thought their iPod was more important and needed to be in USB port 1.
Windows goes "OMG, where's teh keyboard? where's teh mouse? Oh, okay...keyboard's in port 3 now...gotta change everything around..."
Normally when that happens and your computer's logged in, you'll see the "Found new hardware" window for that reason.
However, when you're not logged in, it usually happens in the background and you just have to wait about five minutes.
In other words...BE PATIENT!
...if, for some reason, you can't be patient, then grab a PS/2 keyboard, plug it in, log into your computer with that, and then plug in your keyboard/mouse, waiting for Windows to go through it's "OMG, where's teh keyboardz and mouze" phase.