If your PC is running slowly, it could be more than just cookies.
Hold down the windows key and press R
In the run dialog type
cleanmgr and press enter.
A dialog box to select drive will appear.
Select the C drive (default) and click OK.
When the dialog box comes up, click on Clean up system files.
You will find the same dialog box to select the drive that you got before. Select the C drive (default) and click OK.
It will go and scan again. Once it is done.
Tick the following:
Windows update cleanup
Windows upgrade log files
Temporary internet files
System error memory dump files
System error minidump files
Delivery optimisation files
Temporary files
Temporary Windows installation files
ThumbnailsClick OK
When it asks to permanently delete files, select Delete files.
It will go off and do that. Mine just said it would clean 9.33GB of files. That's a lot but it is the number of files too. Many tens of thousands.
Here is a video of this in action. Note the actual options to check will vary from machine to machine. The size number for each option is important. MB is 1,000 times larger than KB and GB is 1,000 times larger than MB.
Entering disk cleanup has several options. I prefer to go there direct from the run box. He's showing another way.
On a struggling machine this should help out.