Minecraft is making my PC poop

Ever since alpha my computer has had lots of problems with Minecraft, mostly lag issues. As more and more things were added during updates, my FPS kept dropping. Today I found that my Minecraft was having such horrible lag issues that I couldn't even walk for 5 seconds without being teleported back due to lag, because of this I decided to re-install Optifine, to up my FPS by "at least 20". Turns out, that miniscule amount of space that Optifine takes up on Minecraft ruined EVERYTHANNG. As I tried to open up Minecraft I was greated with an error saying: "Not enough quota is available to process this command". When i searched how to fix this, Microsoft support said you need to close all other programs that may be using up your computers proccessing power. Problem is, nothing else was open... Soooo, no mo' MC untill I find a way to boost my processing power. (PS; my computer sucks)

How much RAM and memory is on your comp? or in rather.

Just about 1.8 GB of RAM and just under 25 GB of free space left (out of 200GB)

EDIT: I have managed to open up minecraft once again, but it's still quite laggy unfortunately.

lol. With all the stuff minecraft runs now your def gonna need more then 1.8 gbs of ram. probably about that time to go install so more.

even though you may have nothing open on your desktop, there are a lot of background processes going on. its a pretty easy fix, just open up task manager, go to the processes tab, and close down anything that isn't anti-virus, java or some windows process. Speeds up your comp a CRAPTON. Also, I'd try defragmenting your hard drive and cleaning up your registry. There are a few programs for the registry out there, but the defragmenting software is installed standard. Just go into start>all programs>accessories>system Tools>Disk Defragmenter. It might take a few hours to defragment, but your comp should be a bit faster. Also, make sure your comp is updated, as windows is constantly coming out with stuff to help it run faster and be more efficient. Sorry if this seems really simple to you, but i don't know you're background with computer stuff, so yeah. If you have anymore questions, ask me on skype, my username is Hikazaru37. I can also show you what to click if you do screen share, so yeah, good luck.

OH one more thing: install the optifine mod, or get spoutcraft, on spout craft i got my fps to over 1500, when i normally get about 250, so yeah.

^this

Also, installing more ram should help. Its fairly simple, I know how to do it, as I built the computer I use. If you think youll do that, Google will provide a more thorough walk through than I can but Ill try to give you the gist of it.

Buy Some RAM from Frys or any Other electronic store. Get Anti-Static wrist bands so you dont zap anything. Get a good screwdriver. Unplug computer. Open case. Locate RAM sockets(They are on the motherboard and will be about as long as the RAM sticks). Push back the levers on the end of sockets and click in a few sticks of RAM. Push the little levers back in. Make sure it is all secure. Close Case. Boot up.

Dont try exactly what I said, its just the gist, not all the steps.

you could also try increasing your virtual memory (my pagefile is set to be constant at 16GB)

Kay, I did a lot of what you told me to do (as long as it was simple) and it helped! I can now play MC at 45FPS with no other processes running (and optifine -> everything on lowest/off).
Also, I found something that can boost everyone's FPS by over 9000. Just watch this video and do what he says but for your comp.