I do PC repair on the side and am looking to use a bootable flash drive as a PcRepair Kit. I'm also looking for anit-virus, anti-malware, Data-Recovery, Hardware testing. It would be great if it was embedded in an OS like XP or linux.
PenDriveLinux is a spectacular option. It creates everything you need for the bootable USB drive to repair pc's. You can boot up to a linux build of your choice, or to a repair disk of your choice (i.e. Ultimate Boot CD). Pendrivelinux also has Gparted, DBAN, Avira rescue disk and many other options. It even has an option to setup a windows installation (it says vista/7 but I'm pretty sure you could get an xp install on it too) If you're looking for an all in one, PenDriveLinux multiboot is what your looking for.
The one I've used most frequently is BARTPE. It's a little bit clunky, but can be expanded to include your own tools and generally does the trick. In particular, it lets me access a PC's hard drive and files without having to boot from that drive, thereby avoiding any startup issues, malware, lost passwords, and so on. It automatically tries to connect to available networks, allowing access to web-based tools and antivirus updates.
There is always Ultimate Boot CD for Windows...
UBCD4Win is a bootable recovery CD that contains software used for repairing, restoring, or diagnosing almost any computer problem. Our goal is to be the most complete and easy to use free computer diagnostic tool. Almost all software included in UBCD4Win are freeware utilities for Windows®.