BleepingComputer.com: Can't access Yahoo and other sites directly. Have to delete cookies everytime...more!

Hi. I am currently running a Dell Inspiron E5200 Pentium Dual-Core @ 2.50GHZ with 4GB Ram 32bit Windows 7 Operating System Professional. I bought this computer as a returned item and it worked flawlessly the first 4 months that I had it.I installed programs and used it all the time. I installed NOD32 on it and then a while later I went online with it. Until that point there was no connection to the outside world available for it.
However as soon as I got online I found several problems.
1. I was unable to logon to my Yahoo account. I could always access my Yahoo Messenger though and one day found that if I clicked on the little picture of the mail on my Messenger I could access my Yahoo mail without a problem. Later on,only a few weeks ago I found that I could go into Tools Internet Options, go to Browsing History and click on Delete and I could access Yahoo directly,but only for a short time afterward. Later on,I also found that I could do the same,but ONLY delete cookies and this works exactly the same! (I'm sure I'm close to the problem at this point!)
2. I had the same problems at Flikr and YouTube where I have account and the same delete cookies works fine.
3. I have also had a problem going to some sites where it asks me to select a store location and when I do,it "cycles" around and puts me back at the same screen as if I didn't answer,like an F5 refresh. I have also had this "cycle" happen when a site like Yahoo asks for my password. I put in my password and it cycles or refreshes and shows my handle still there,but now my password is gone. If I type in the WRONG password I do get an error message,so I know my password is right,once again when I delete cookies,the problem goes away.
4 On YouTube I frequently will watch videos and go to add them to favorites only to be told "You must be logged in to use this feature." That's when I notice that I am no longer logged in,and didn't do that on my own.
5. Yahoo Messenger is unbelievably slow when typing a message,letters will not appear for 5-10 seconds. Makes for typing if you watch what you type insanely hard.
I have also had the following problem:

Setup
Setup was unable to create the directory "C:Users\?".

Error 123: The filename, directory name, or volume label syntax is incorrect.

((((This was an error message the I received on 3/12/10 when I tried to install a registry cleaner. I first tried off of the download,but then I ran the program straight off the website because I could not install it from my download location.
I will go into further details on this error on another post,unless it is deemed relevant by those reading this,as I read the rules and they stated not to put multiple errors on one post. But I am suspicious that both problems are caused by the same thing.
Thanks everyone for reading this,it's been a challenge to many people. I could trash this computer and pick up another easily,but I could use the money for other things and I am curious to what's wrong.

This post has been edited by Rackin MyBrains: 03 May 2010 - 02:20 PM