With Windows 10 not far away, and Microsoft promising that it will be a free upgrade for many, now is as good a time as any to be considering adding some more RAM to your PC. Any computer that's modern enough to currently be running Windows 7 or 8 should be fine for Windows 10, but having more RAM always makes sense. It's the most cost-effective way to speed up your PC.
Although most online RAM chip vendors provide a useful lookup system so that you know how much RAM your PC can take, and what type of memory modules it uses, you'll still need to take off the case to check just what RAM is currently installed. Won't you? Actually, no. If your PC supports Serial Presence Detect, you can find out all the relevant detail without needing to take out a screwdriver.
One excellent software utility that supports SPD is called CPU-Z. You'll find it at http://www.cpuid.com/softwares/cpu-z.html and it's a 2 MB download. Go for the Zip-English option, and you'll end up with a zip file which contains portable versions of both the 32- and 64-bit software. The program is malware-free according to VirusTotal and Web of Trust.
Run the program and click onto the SPD tab, and you'll see something like the image shown below. This is from my own PC and, as you can see, tells me precisely how many slots my machine has, whether there's a memory module in any slot, and exactly which component is in the slot. So now it's easy for me to locate empty or under-utilised slots and to buy additional RAM to fill them.