What other useless files can I strip out of Xp?
Assuming that you create regular image backups of your SSD, here are a few other things to consider to reduce XP disk space usage :
1. delete all "$NTUninstallKB...." folders from the "Windows" folder
2. if your disk files are not already compressed, then you can save some space by compressing the following folders within the "Windows" folder : $hf_mig$, assembly, Installer
3. navigate to "C:\Windows\Software Distribution\Download" ... if there are files there, delete them ... unless you are currently downloading/installing Windows updates
4. navigate to "C:\Windows\system32\config\systemprofile\Local Settings\Temp" ... if there are files there, delete them