XP Reinstall keeping old files question

I did a reinstall of Xp and not knowing what all the choices were, i selected to reformat an existing partition which I now know rewrites XP but leaves other files intact. My purpose in reinstalling was to clean the machine to try to speed it up by fully removing un-needed software. I now know that I should have deleted the partition and then instaled Xp.
So now I have updated to SP3 and installed a bunch of stuff taking two days to get to this point and now I find my old files still there and so are the programs. None of the programs are listed in "add/remove programs" but the files are there and they do seem to run though any purchase codes are gone so some are asking for that before allowing me to use fully.
Looking in the registry, I don't see entries for all this software except for the three I started as mentioned above.
Can I simply delete all the folders and files for all this old software and just reinstall the few I now want (and defrag) and accomplish what I wanted originally or do I have to go all thru the reinstall, update, etc mess again?
Can I leave these old programs alone (the ones I would just be reinstalling) and expect them to run right (remember they have no registry entries and are not in "add/remove" so apparently not really installed (but will seemingly run)
Thanx for any advice on my mess...........at least it is running....yeah
LB

 

A format would delete ALL the files on that partition irrespective of whether these are programs file or data files.

There is no need to delete the partition unless you want to increase or decrease the size.

It seems that you have installed Windows on some other partition than in which it was originally installed.

I think you can, but as Steve pointed out, it would be better to reinstall.

If you have enough disk space, you can leave them there but don't expect any of these program to run or behave properly as they have their parts missing in registry & most probably in Windows,System,System32 directories also. Plus in future, they may also create problems/confusion when you want to install these.

Nobody learns without creating a mess, so don't worry