Win XP cleanup

I have multiple old computers in My shack. All hand me downs which I've spent time cleaning up the OS of each and try to make them useable. I recently inherited an  upgraded laptop when My wife received a new one for Christmas. Its a Dell Vostro 1520 running a free download of Win10. A nice laptop with Win10 and definite improvement over My other older PC's running XP.
  My main PC is a desktop Dell dimension 2400 running Win XP. Big hard drive with plenty of room and just enough RAM to make it fairly speedy for an old PC. Last week I noticed it was no longer speedy but incredibly slow--virus? malware?. Not sure but since it has 99% of My Ham radio life on it, I wanted to attempt to save it.
  I've always known the old XP is slowly running out of time--lots of programs it no longer supports but I wasn't ready to junk it yet. I decided to try any and all means to save it. While running various virus,cleaning,malware programs I started to add Ham Radio related programs to the Win10 PC in case My attempts at saving this one were not successful. New N1MM, new loggers, sound card RTTY ,etc. During this time I ran anti-virus several times on the old XP----slow,slow slow.Painfully slow! Then tried cleaning and malware programs. Deleted unused programs and did a defrag of the hard drive and MS disk clean.The speed of the PC I noticed increasing as each program was run-sometimes multiple times. During this time I also restarted and powered down several times.One of the power cycles I took the time to open up the case and vacuum clean the dust bunnies out.Lets just say they had babies big time!!!
  I also reseated cards and memory along with various ribbon cables. After all the maintenance both software and hardware I now have a speedy( for XP) PC again.I can't pinpoint one remedy but think the combination of everything was the key. I know its days are numbered but for now its actually seems faster than before! OK-maybe wishful thinking!
  73---Tim
PS-not much to advertise but I used all free shareware programs along with Microsoft software included with XP