the clean up steps are not optional, they should be done on a regular basis.
disk cleanup, disk defragmenter, clean caches.
Also, please answer the first questions I asked, current antivirus, Service pack of OS, make-model-and model number of pc.
also look in Device manager and see if any errors are there and your drivers need updating.
go to Microsoft updates and do a high priority scan and install all.
then do a custom scan and look for any rootkit updates and install them.