Desktop.ini are system files. They hold configuration information on how you want that folder displayed. Don't worry about them, they are supposed to be there, and as you figured out, when you delete them, windows will recreate it.
The slow system performance can be caused by several things. First you have 2 AV scanners. They will fight each other. It is best to get rid of all of them but one. Be careful of AV scanners that hid on other applications. Lavasoft AdAware has a virus scanner in it, for example. Also if your have a lot of temporary files that can also cause the problem (CCleaner from Piriform.com does this really well). These include leftover files from installers and windows update, internet cache files, log files etc. If you have taken care of both of those things, then you may want to try running chkdsk on your drive, and then defragging the drive.