|There are two types of external USB optical drives|
- larger ones that use desktop drives that require an external power adapter to be connected to the external case - that external adapter must be connected and must be working properly (it supplies 12v, at the very least to the optical drive itself).
- and smaller, slimmer ones similar to those used in laptops that do not require an external power adapter to be connected to the external case (the optical drive plus the external enclosure's circuits draws less current, needs only +5v) .
What I'm trying to get through to you is, for either type, the USB cable must be plugged into a USB port that can actually supply 500ma (at +5v, the USB port's voltage) - e.g. a port built into the laptop, not one in a hub connected to one laptop USB port, even if that hub has an external power supply, is a lot more likely to be able to supply that. (Some laptops / netbooks cannot actually supply 500ma from one of their built in ports - you must connect the external hard drive or external optical drive to TWO USB ports, or if it's the "slim" type of optical drive or a 2.5" external hard drive, into one USB port and plug an external +5v power adapter into the external enclosure). It's the motor inside the drive that requires the lion's share of that 500ma of current, so, when you insert a disk, the drive motor spins, and the drive draws a lot more current.
The first disk of a "Restore" or "Recovery" disk set for a brand name computer model that has XP on it is usually a slightly modified OEM XP CD. In that case, all the files and folders on the CD are the same as those with the same names on a regular OEM XP CD that has the same SP updates included, or no SP updates included, for the same version of XP, Home or Pro, except that the internal contents of some of the OEM.* files are different.
I've been told by one guy that when you boot an XP CD from an external USB optical drive, all you see is a blue screen, and I found several references on the web that booting an XP CD from an external USB optical drive doesn't work.
The other disk(s) in that type of "Restore" or "Recovery" disk set are NOT bootable, and the first disk in the set does NOT prompt you to insert the second disk, etc. In that case, the other disks usually have Drivers for the devices your model needs, and sometimes Applications (programs) that were included in the original brand name software installation too, that are not built into Windows
If your Restore" or "Recovery" disk set is the older type of set, a set of disks you must install as set in order, the first disk is the only one that is bootable, and the first disk in the set prompts you to insert the second disk, etc., then they should install fine from a USB connected optical drive.
If your computer has an XP MCE version on it, it's more likely your disk set is this type of set.