Now, I can't even listen to a song from UTube without the computer buffering 4 or 5 times during one song.
You did not mention what operating system you're running (I presume it's a version of Windows)...
there are several things you may need to do... first off I would suggest getting rid of the "Windows" firewall and install a third party application...I suggest:
Firewall and AntiVirus Free Software Download from Comodo
this will let you monitor what your internet connection is doing and what programs on your computer are using the connection...beware, if you are not running a quality firewall other progranms on your computer may be using bandwidth and slowing down your connection...
another one of thefirst things to do is become familiar with what services and processesses are running...This is very important...
Open the 'Task Manager' and click the "process" tab...starting at the bottom of the list look at the process list by searching (Google) you can find a list with explainations for each one...some may actually be spyware or malware that will greatly slow down your internet connection...search by operating system...i.e., Windows XP, Vista etc...
A prudent computer should learn what processesses are running and whenever something does not seem right check the list for suspicious entries... especially beware of processesses that have .dll or .exe extensions...
You can prevent unwanted or unneeded services and processes from starting by using MSCONFIG
Once you install a quality firewall like 'Comodo'...as soon as you start the computer...it will alert you to any service or process that is trying to use the internet connection...generally the only programs that need to use the connection are your web browsers (Internet Explorer , Firefox etc.) and your e-mail program...along with anti-virus applications that need updates...
There are several quality (free) programs that will help you get rid of intruding spyware and malware...but there are many more that are actually spyware or malware themselves...rather than trying to list them here I suggest visiting a reliable computer support forum and check their indexes... PM me if you want some suggestions...
good luck