I don't know any sites from which you can learn much about Windows and things like that.I learnt a lot about that by myself through the past 14 years.
Of course I am not saying that you need 14 years to learn all that.I needed that much because I was a self-studier.Besides every 2 years there would be new Windows OS lol...
Well for the start I would recommend you to learn english language very good.Without that you can forget about other things.But I am pretty sure you know english language pretty well so all other things should not be a big problem.
Second you MUST learn,use and investigate all older Windows OS versions such as Windows 95,98,ME and so on...so that you can get a better idea how to make something faster and more simple on newer Windows OS versions such as Windows XP and especially on Windows Vista and Windows 7.
Third you must learn and make your own ways how to make programs,games and all other things to run the best as they can under the smalles amount of RAM such as for example 512 MB of RAM DDR1,WITHOUT ANY OVERCLOCKING!!!!!!!Is it worth buying new computer every lets say...2 years plus upgrading its components during those 2 years???No its not.The idea is to make your computer and ALL programs and games on it to work great on very weak specifications.Once you accomplish and learn this,you WILL NOT NEED to spend much money on buying new components or even totally new computer...Also you won't have any need to upgrade your OS because when you have knowledge,you can accomplish miracles even under Windows 98.Once you have knowledge,you won't care about the OS look or how old it is.Of course I am not saying it has to be Windows 98.Pick your favorite Windows OS and stick with it as long as its possible to do EVERYTHING you need under that OS.Many people will say that this is bullsh!t,but don't listen to them...They are stupid,not you.
Fourth is to learn what ALL THOSE OPTIONS in the Windows OS,drivers and programs are for.Its not enough to just install Windows OS,drivers and programs you need.Most of it contains many useful options,especially the Windows OS and drivers.Having knowledge about those options and configuring them ALL properly will improve your computer speed A LOT!
Fiveth is to learn how to properly format your entire HDD so you can make the most fresh install of your Windows OS version.Its not enough to just delete partitions and then install the Windows OS using its CD or DVD-ROM disk...
Sixth is to learn how to fully protect your computer from any possible threats and all kinds of viruses,adwares,spywares,dialers,trojans and so on...Its not enough to just install the Antivirus.You must configure its options one by one properly and know what every option is for...You must also know how to use the Antivirus software on the way its NOT slowing down your computer while you are using certain programs,playing certain games and so on...
Seventh is very important.Windows OS has many useful tools in it.With those tools you can make many things you need WITHOUT DOWNLOADING CERTAIN PROGRAMS WHICH DO THE SAME THING!On that way you are installing unneccessary programs and your registry is becoming bigger and complicated more and more...
Eighth is to learn how to use DOS.At least those basic functions.DOS can help you a lot and save your life many times.Many people will say that this is bullsh!t,but don't listen to them...They are stupid,not you.
Nineth is to find your own and the best way how to clone your entire HDD in the case your Windows OS suddenly stops working WITHOUT USING ANY CERTAIN PROGRAMS FOR THAT!Almost everyone I know use programs for cloning the HDD and most of them are doing that directly from the Windows OS environment.This is VERY BAD way since in many cases it can happen that later when you are returning the cloned HDD back that it doesn't work at all and then you lose your entire Windows OS,all your adjusted settings,all your data and so on...........In order to learn this,you must also learn what is the BOOT SECTOR and how to fully format it before making the new one with the Windows OS CD or DVD-ROM disk.Once you learn this,you will also be able to know how to transfer your ENTIRE HDD from one computer to totally different computer WITHOUT INSTALLING AND CONFIGURING THE WINDOWS OS,PROGRAMS,GAMES AND SO ON!

I am sure that installing the entire OS,installing and configuring EVERYTHING on the new computer is a huge pain.Well if you learn all this,you will need to do that just one time in your life and then simply copy all that from one computer to all other computers you have.Many people will say that this is not possible and that is bullsh!t,but don't listen to them...Just ignore those kind of people.They are too bored in their life and probably very jealous...
Tenth is to know what each part of the computer hardware is for such as the HARD DISK DRIVE,PROCESSOR,GRAPHIC CARD,RAM and so on.....................
Well thats about it.In very very short I told you what you must know in order to use your older computer much better and faster then those people with the newest computers...I didn't mention many things because I dont want to make my post too long.
One more thing ---> TRUST TO YOURSELF AND NEVER GIVE UP.ALL THOSE WHO TELL YOU THAT YOU ARE SAYING AND MAKING BULLSH!T AND WHO ARE SAYING THAT YOU ARE STUPID AND DON'T KNOW ANYTHING,JUST IGNORE THEM.ALWAYS REMEMBER THAT --->YOU<--- ARE THE ONE WHO CAN ACCOMPLISH MIRACLES ON OLD AND WEAK COMPUTER FOR THE DIFFERENCE OF THEM WHO ARE BUYING NEW COMPUTERS AND NEW COMPUTER COMPONENTS EVERY FEW MONTHS.

KEEP IN MIND THAT --->THEY<--- ARE SOLVING EACH PROBLEM BY REINSTALLING WINDOWS OS EVERY TIME FOR THE DIFFERENCE OF --->YOU<--- WHO SOLVE THAT PROBLEM IN FEW MINUTES WITHOUT BUYING AND REINSTALLING ANYTHING!
Cheers mate and MERRY CHRISTMAS!!!