Do you have a USB port? If so, you can install from a memory stick one of the smaller distributions (damn small linux, etc.) and there may be a USB stick version of Ubuntu or others as well.
That said, without a CD and without an internet connection it will be difficult to update and maintain ANY operating system you can have on it. So maybe it is worth investing in a USB-CD/DVD device.
How did you maintain windows all these years on the laptop? You can't install updates without either a CD or an internet connection. True that without the latter you can manage without the patches and security updates, but still, one wonders.
Check out my web site - www.words2u.net