It’s possible that the issues are due to older versions of flash and/or java. Use of these resources is wide spread and browsers will flake out if using an outdated version. Well, more accurately, the computer will have problems if the version of these is notably older than what the web page(s) require. Try updating both.

That said, ideally at some point you’d re-boot the computer and looked at the task manager, under processes, to see what’s running. After that, use the computer as you typically would for a while and then look at the processes again. One or more processes will use a lot more memory over time. This is the likely culprit.

Another possibility is that the browser had some add ins that have substantially slowed response time. With IE these would be found under tools>programs>manage add-ons. I dunno where they’d be with other browsers.

It’s also possible but unlikely due to the description that increasing the size of the system page file will help. Given the small amount of RAM, increasing this will not hurt.