|Wanderer is correct. Once you have installed Windows XP it needs to be activated. This can be done either over the Internet or by telephone quoting the product code you entered when Windows was installed. You have thirty days to do this. If you don't, then Windows XP will cease to work.|
Continually reinstalling Windows without activating will mean that it will cease to work every thrifty days until you do activate it. All you need to click on the activate now before the thirty days is up. If you have a legitimate copy of Windows XP it should take no more than a few seconds. If it is a pirated version of Windows then you may have problems.
Without a CD drive you are going to have difficulties. How you are going to resolve that problem I have no idea as I have never had a computer in the last fifteen years that did not have a CD drive.