SFC in Windows XP will look in Windows\ServicePackFiles\i386 for updated files. It will not remove/delete existing patches/hotfixes or service pack files.
It asks for XP CD (when running SFC) to retrieve files that was not updated or changed by the patches/fixes or service pack files.
That is true if you did not delete the content of ServicePackFiles\i386 folder
3rd party application should not be touched by SFC. SFC scans for Windows "system" files only to verify whether it was altered or damaged. It will retrieve for the undamaged copy from the ServicePackFiles folder or XP CD installation disk.
The feature in XP that "may" (not always) remove your patches/fixes or service packs files is the "Repair Install"
Due to several memory dumps and other problems from files I'm unable to un-install, I am considering SFC run & fix. If I do this using XP Pro SP1 disk what will happen with the 9 or 10 asst'd Hotfixes currently installed?? Will all be eliminated back to SP1 and would the same be true if I installed SP2 first and then ran using SP1 disk?
What about various programs such as Spybot which have their own hooks in the registry such as Sartup tool over-riding Ms config , or CCleaner 's lines into various parts incl. Mozilla. Will they be disconnected/corrupted failing to work or possibly be un-installable from missing connections? Will they have to be fully re-installed ? A little hesitant to say least!