Setting up wireless, Im confused!

I got a new wireless router(Bt voyager 2091) and WOW my speeds have shot through the roof!, im not sure if its linked but I think I had a USB power problem(now using ethernet till I get wireless sorted!) I put a wireless card in my desktop and I already have one in my laptop.

Basically how do I make it so my connection is secure and not stolen(I live in a area full of chavs so reckon one of them will steal it)

Also what does VPI and VCI mean? it told me in manual to change these to 0 and 36(Which I did) and as I say compared to my USB modem it is VERY fast(even better than the 6.5 connection I was getting off peak)

As for the USB problem(which is now sorted!) it was working ok, when it was just a USB keyboard and mouse, but as soon as I put in a USB HD(which I borrowed from a friend) my keyboard and mouse constantly didnt work, but now without the modem it works great!

Also the manual says the router username and password is admin, how do I change this!

Right I tried XP's one and it gave me option for flash drive or manual, I tried flash drive and it tells me to install it to my wireless access point? theres no USB port on my router!