[CentOS] Strange: wireless card shouldn't work, but it works ?!?

Hi,

I know this is a rather unusual request. Normally, people would complain 
about a card that *should* work, but here goes.

I have a series of machines in a computer room, all equipped with a 
RT2561 wireless card. CentOS doesn't include support for that card, so 
what I usually do to install a system:

1) Install a *very* minimal base system (the bare minimum).

2) Install some development tools (gcc, kernel-devel) from the CentOS 
install CDs.

3) Copy over the driver source (rt2561-cvs-daily.tar.gz) downloaded on 
another machine.

4) Compile that driver and install it (plain make && make install).

5) Configure my network to use the wireless card.

6) yum update my base system once I have network.

This method has the advantage of avoiding having to pull 20-meter 
Ethernet cables only to configure wireless :oD

Now one thing puzzles me. I have the install CD set from 5.0. The 
default kernel is 2.6.18-8.el5. Once I updated the whole base system and 
rebooted on it, I'm using the updated kernel, e. g. 2.6.18-53.1.4.el5 at 
this date. As far as I understand, each kernel has its own set of kernel 
modules under /lib/modules/`uname -r`. A quick ls on /lib/modules 
effectively shows me the two directories for the two kernels.

I installed my wireless driver on the old kernel, which means normally 
after rebooting I'd have to build and install it again for my new 
kernel. Bu strangely enough, when I reboot on the new kernel, my 
wireless card still works without me having rebuilt the driver.

I'm clueless about this.

Niki