USB.inf -

Microsoft Support Engineers seem to assume that everybody has a genuine bootable XP installation CD with Service Pack 3 on it.

The fact is, that most people that look for help in the MS Answers forums have never seen a genuine bootable XP installation CD in their life and wouldn't be unable to get their hands on one.  It is extremely unlikely that "your manufacturer" will send you one of you contact them, but that always seems to make it into the advice sooner or later.

MSE replies that have links to KB articles or other ideas that begin with "insert your XP CD-ROM..." usually don't go very far after that and somebody else has to step in and really do the fixing/helping.  That is a shame.

The usb.inf file is also not one of the 3498 files that Windows File Protection looks after, so there is no backup copy on your system.

I uploaded a copy of the XP Pro SP3 file you need to my SkyDrive (everybody has a SkyDrive for sharing files).  I think it should be the same for XP Home SP3.

You can download it and when you do, put a copy of the file in this folder (assuming Windows is installed on your C drive):

c:\windows\inf

Here is the link to my SkyDrive and you can look for the file you need there:

http://cid-6a7e789cab1d6f39.skydrive.live.com/redir.aspx?resid=6A7E789CAB1D6F39!311

When you download the file (especially if you use Internet Explorer), when you get a chance to save the file, it may not save the file with an extension (like .exe, .dll, .cpl, .sys) so you will have to manually add the proper extension to the file when you download the file before you save it.

You can download the file with no extension and then rename the file to add the proper extension.  You don't want to try to use a file called usb when the file name really needs to be called usb.inf (if the downloaded file has no extension you will have to change the name of the file to add the proper extension to get it to work.

You need to put the downloaded files in the correct folders on your system.

I don't know if that will resolve your issue or not, but at least you will not be missing the file.

USB.inf should be in \windows\inf (%systemroot%\inf actually).  Who manufactured your system?  In most cases, you can (and should) generate the installation and/or recovery CDs/DVDs.  What Service Pack level is your Windows XP Home Edition?