might need to upgrade your RAM, cuz if it is ram, it must be really low to not be able to open a page, no matter how big it is. it could also be spyware/adware causing your computer to run slower, it could be a virus, it could be registry problems, it could even be your computers settings aren't set right, causing it to run half-assed or not at all...

http://www.safer-networking.org/en/index.html
Spybot Search and destroy, download and run this (after fully updating it), after it's finished, make sure everything is selected, and click Fix Selected Problems. if it asks you if it can run spybot when you next restart your computer, click yes, and restart, as some things may be in use once your computer is fully started, and therefore, unable to be removed.

http://www.ccleaner.com/ccdownload.asp
Crap Cleaner, download/update this fully as well, then under the Cleaner > Windows option, click Run Cleaner, after that's done, then click on Issues, run a scan, and if anything comes up, make sure it's box is checked the click Fix all selected problems.

http://www.hoverdesk.net/freeware.htm
Regseeker, download then go to Clean the registry, make sure all the boxes are checked, then click 'OK!' when it's done, click Select All > Select All, and right click, then click Delete.

you also might wanna run a virus scan, but in this day and age of computers, it's only about 200% more of a chance that the problem lies within Spyware/Adware, rather than viruses...