What Ubuntu is best for Lenovo Laptop?

[GaryTaig]

We have a Lenovo Thinkpad that runs WinXP and I want to load the most 
suitable version of Ubuntu.  Not necessarily the latest.

ThinkPad R500
Core 2 Duo P8400
2.26 GHz
2048MB RAM
BIOS V207 (Feb 2009)

Is there a Ubuntu that's likely to load and run without mishap?
I'm not keen on the latest; 14.04 sounds nice but there is no time for 
experimenting, or trying to discover why a broken installation isn't 
working.

It will be used on the Internet, has WiFi and Bluetooth etc. and can 
boot from a CD.  Has plenty of USB slots but appears NOT to be able to 
boot directly from USB... only from a USB diskette.

Is Ubuntu the most suitable?  I've been running it on a desktop machine 
for several years, I think the first version was about 7 or 8, currently 
10.04 LTS.

What is Kubuntu?  Have seen it mentioned but never gave it more than a 
passing glance; always snowed under.

Is there a Ubuntu specifically for Laptops?  Perhaps one needs to cast 
the mind in a wider arc?

Any help, leads, pointers greatly appreciated.
GaryT