Computer running Slow?

Mine perked right up after I uninstalled (zapped) the Avast free anti virus.  I'm still running XP, and after blowing away Avast, it now runs faster than Win 8 on a much newer computer. 

Antivirus on Win 8.1

Flatbeast, my new Win 8.1 laptop came with McAfee antivirus installed.  It was a freebie trial installation with a drop dead date.  Either pay up or it drops dead.  Although McAfee is good name in antivirus, that goes way back, back even before Windows, it's expensive, and slow and I have been having good results with Avast which is free. 
   So, when McAffee  dropped dead today, I uninstalled it.  What used to be "Add and Remove Programs" has been renamed to "Programs and Features" but the Microsofties didn't move it, it's still on the control panel where it ought to be.  Removal was a major effort, taking minutes and a reboot.  Uninstalling was like pulling dandelions, they will come up, but they don't want to. 
   So I downloaded the free AVAST, no sweat.
   So I checked on my RAM usage.  With McAfee installed, I had 1846 MB of RAM used.  After uninstalling McAfee RAM usage dropped to 1289 MB.  That's 557 MB worth of antivirus code that used to be hogging RAM.  That's a lot of code.  Flatbeast feels a bit more lively after removing all that baggage. 
   Installing AVAST pumped RAM usage back up to 1570 MB, which is still 270 MB better than McAfee.