Upgrading an iMac from Tiger to Lion

[Mole]

Hello,
I've been given the task of upgrading my neighbours intel iMac from 10.4.11 (Tiger) all the way to 10.7 Lion.
I'm not that clued up on Macs, so need a bit of help, especially with regards to backing up everything, and from what I gather, installing Snow Leopard then Lion, as Lion won't install on anything below 10.6.

Any simple programs etc that I could use to backup everything that is on it, then restore once everything is finished?
Unfortunately not everything is in 1 place, documents and photos wise, and despite asking them to tidy it up so I can just drag it onto an external drive, they haven't.

Thanks

 

[Adam.]

I've installed a few tigers to SL this week and just whacked the CD in and clicked install. All files were intact.

If you don't want to risk it then run a time machine backup.