System very slow

[kubicle]

You have 2 GB of RAM but only 160 MB is free... that seems pretty low. Unfortunately, in the output you posted from top...

There is actually around 800 MB available to applications, page cache will be dynamically freed if applications need it.

-/+ buffers/cache: 1257464 806836

[SteveRiley]

In KsysGuard: pluginloader.exe takes 89% of CPU and Firefox hogs the memory.
How do I know which plug in is it loading? is it possible that it's flash?
but then how can I watch videos without it?

pluginloader.exe is part of Pipelight, a version of Wine that embeds the Windows binaries for Flash and Silverlight into Linux desktop browsers. This could very well explain why you're running low on memory, as you're simply loading lots of processes into RAM to accomplish this. Unless you're watching Netflix, you really don't need this, as nothing else on the Internet uses Silverlight anymore. You can still install the Linux version of Flash, but it's old (meaning some videos won't play) and at some point Adobe will stop supplying security updates for it.

There is actually around 800 MB available to applications, page cache will be dynamically freed if applications need it.

Right, I always forget about that one.

[kubicle]

Right, I always forget about that one.

Of course, the swappiness setting will control how aggressively the system frees the cache. With a high setting the machine might decide to go swapping even if there is cache to be freed, so your remark is still relevant.