Google is your friend.  $25 from Walmart.  I don't usually buy anything from Walmart, especially electronics, so your mileage may vary.

https://www.walmart.com/ip/4GB-2X2GB-DDR2-MEMORY-FOR-Compaq-Presario-CQ60-Series/481195318?wmlspartner=wlpa&selectedSellerId=7952&adid=22222222227076875357&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=189616769695&wl4=pla-348800467607&wl5=9022467&wl6=&wl7=&wl8=&wl9=pla&wl10=115793534&wl11=online&wl12=481195318&wl13=&veh=sem

If your machine is old enough that you are on 32-bit you can't do more than 4GB RAM.  The processor and motherboard may also have limitations.