Some computers have the ability to boot from a USB flash drive, but that's something you'd have to check into. Otherwise the only alternative to burning a CD is to use a floppy drive, assuming you have one laying around and a way of connecting it. In any case, DBAN is the application I would suggest using to wipe the hard drive before installing XP.
P.S. Note: If that is a SATA hard drive you may need to request additional XP (SATA) drivers from Lenovo for the XP installer to 'see' the hard drive.
Lenovo sent me the disks foe WinXP which I paid for. But the Boot disk for it which should erase the hard disk gets hung up with error 999 at the very same spot every time. So they sent me a new set of disks. Same thing. After many talks with techs. it was decided to erase the hard drive and they told me how to put the Data Disk thing onto a CD and then boot up with that. As I was crashed ....again from trying to use the WinXP boot disk, I had to put Vista back on so that I could erase it and then put the 5 Win XP disks in. But that doesn't work either. Can someone tell me how to erase the hard disk without having to make a CD to do it?