Hi kanem, first off, yes, Live 8 all day every day - I like that one!
Second, there are a few options if you're looking for strings. First off, under Instruments->Instrument Racks, you'll see some string presets (how many depends on which instruments you own). Additionally, many of the Ableton Instruments have string presets. You might also check out the free Live Packs available for download, some of which include string sounds:
http://www.ableton.com/livepacks
There are also some great options for purchase from Ableton, if you're looking for some serious strings:
Tension - a physical modeling string synthesizer, developed in collaboration with Applied Acoustics Systems. More info and sound samples here:
http://www.ableton.com/tension
Essential Instrument Collection 2, which includes some great sampled strings (some of which come from the Orchestral Strings library), as well as brass and woodwinds:
http://www.ableton.com/eic
Orchestral Strings - a comprehensive selection of solo and ensemble violin, viola, cello and double bass, all recorded in their natural positions within the orchestra, complete with a number of articulations:
http://www.ableton.com/orchestral-strings. Also, note that there are companion libraries with brass and woodwinds.
Hope this helps! Note that you can try out Tension for free with a 30-day trial license of Ableton Suite 8.