As to making it load faster, no extensions would be able to help, adblock helps ALOT with the rendering speeding up when it hides the advertisement element, so thats helps, but it doesn't make it faster loading, it technically makes it slower. XD
To keep my computer running 100%, despite it being 4-6 years old (It has somehow out-done our desktop!) I am sure it's because I run the program called CCleaner, it basically clears all unnecessary stuff from your computer, like some history, recycle bin, and other stuff that takes alot of space but isn't needed. I run that about once every 2 days. I usually empty 100MB-500MB of stuff, which frees up a chunk (Most) of the ram. Then I always defragment my laptop once a week. To get to Windows's defrag program, Click Start->All Programs->Accessories->System Tools->Disk Defragmenter. If you have never ran this, you might want to pick a day you don't want to use your PC and run it. Dependeing on how bad, It might take 20 minutes or so if you do it regularly. If you have never done it and your computer is older, It may take Hours to DAYS. That will make it run great after a good defragment. Then for no reason I run disk checker to let the drive know where it is bad before it hits that track and finds out later. Then I reboot my PC from absolute zero. Power down, press start, let it load up and it should be as good as new.
Another things is to eliminate any programs that run in the background at all. I have none, but if I had, say, AIM Limewire (Limewire is BAD FOR YOUR HARD DRIVE!), My computer would be half as fast the entire time. Hence why I don't have any background running programs. And also, go through your programs on your PC too. Get rid of the ones you don't need or use.
The way I do it is Remove programs, run CCleaner and then CClean the registry, Defragment the drive, Disk check, shut down.
That is the best thing you can do for your PC.