A clean reinstall will fix any software issue which is what it sounds like you have. A dying hard drive or bad memory/motherboard can cause slowdowns but they usually cause crashes instead. A processor going bad without overclocking or some kind of catastrophic hardware failure or power surge is very uncommon.

I haven't got any crashes at all and haven't overclocked anything so if re-install wont fix it then it must be a hardware issue

well.. off to backup few files and format

I haven't got any crashes at all and haven't overclocked anything so if re-install wont fix it then it must be a hardware issue

In computers we say: does not compute.


If fan spins up, something pegs the CPU. Use Process Explorer to find which process or thread it is when it happens.

If fan spins up, something pegs the CPU. Use Process Explorer to find which process or thread it is when it happens.

Trufax.

Why are you so determined that it is a hardware issue? Hardware problems rarely cause slowdowns; more often they cause crashes, fires, or irreparable damage.

Not that formatting is bad, but it's a huge step to jump to before doing more research into what is happening.

In computers we say: does not compute.

If fan spins up, something pegs the CPU. Use Process Explorer to find which process or thread it is when it happens.

Haven't formatted yet. Ok I did that: winamp, few folders and copying files from another folder to one at the same time.. I tried morrowind on fullscreen, the fps dropped again and had weird lag, when fps was normal it sometimes was like "warping" forward but fps stayed normal. but when I played on windowed it ran smooth the whole time.

Here's a screenshot, my system is in Finnish but the window at left top corner tab reads "Prosessit" which is "Processes" in english ( 'raw translation' )
and "Järjestelmän vapaaprosessi" is in raw translation 'System freeprocess' (dont know the right translation).

edit: "Suoritin" = "Processor"


But yes, in windowed mode: everything seems fine. In fullscreen mode: not.
Same happened with Call of Duty Modern Warfare


So.. my GPU is acting up?

edit2: "Järjestelmän vapaaprosessi" is in raw translation 'System freeprocess' is all the time +80 under processor. is that normal?

I vote against a heat problem. Throtteling due to excessive heating would only occur well after your fans have spun up, unless you have overridden your fan settings not to kick in until a ridiculous treshold. This throtteling should easily be visualized by some of the available tools.

Your problem is obviously some background process. Somewhat ironically, my first suggestion would be to uninstall all the anti-virus crap you installed.

Checking your active processes while running your game windowed is a flawed test; this will likely force your game into the same refresh rate as your OS, thus altering your load profile. Better to save your process activity to a log file.

Either way, forget about the anti-virus scam, and start thinking about system restore.

As a general rule: every year (or more frequently if you wish; I do it ever 6months or when necessary) do a clean install, reformat everything, and restore anything vital from backups.
As far as anti-virus goes... I use Kaspersky. I rarely have problems with viruses sneaking up on me

I cannot agree on either of this. Doing a clean install once per year is destructive, time-consuming, and unnecessary. Do a sane setup once with sane security settings. Don't run your webbrowser with admin rights (better yet, run it either in a sandbox or as a user that can only write to a single folder). Don't surf porn sites all day, and don't open every [font="Courier New"]awesome-tits.jpg.exe[/font] file that an unknown person sends you per email. Do not download and install every shit only because it's free. If you do, try it in a virtual machine first.

Then, seriously, you don't need to reinstall regularly.

Also, Kaspersky is easily able to make the fastest computer unusable, especially (but not exclusively) when you do software development which involves launching a lot of programs and modifying exectuable files. Seriously, Kaspersky is worse than some malware you might otherwise have on your computer.
You cannot even configure Kaspersky to be less abrasive and invasive, and less braindead. Even if you turn off live scanning entirely, it will still regularly freeze your computer mysteriously for 10 seconds (with no notification whatsoever), it will still scan newly modified files (i.e. after each and every compile!) or files of which Kaspersky believes that they've been modified (files that provably have the same SHA-1 and modification date when you look at them), and it will still regularly block you with false positive alerts on entirely harmless programs (which suggests it probably misses the real ones...).

edit2: "Järjestelmän vapaaprosessi" is in raw translation 'System freeprocess' is all the time +80 under processor. is that normal?

If you have a modern processor (quad-core as you say) then that's just ok (TES consumes 1 processor at 100% --> 25% system load MAX on a quad thread machine).

To be completely honest, I'm somewhat confused. Having a load so low would seem to rule out overheating...
However, if this has integrated on-die graphics then there might be the chance the GPU is overheating so much that pulls the envelope while leaving the processor free... but I guess that's unlikely for your system - by the way, it might be useful to know when (at least year) you bought it!

I fixed computers exclusively for 2 years of my life. I could count the number of hardware failures that caused computer problems on one hand.

Don't waste your time doing any hardware diagnostics until you do a clean reinstall of windows. If you do a reinstall and then it's still slow then you can start diagnosing what part is malfunctioning. Most common parts to fail are hard drives, power supplies, and RAM. I've never heard of a processor that was installed properly, that was working OK, wasn't OC'd and then suddenly "broke". Not to say it can't happen but would be very uncommon.

I imagine the "System free process" is probably the "System idle" process.

Have you updated your GPU driver recently? If so, perhaps it is buggy and causing a slowdown. If not, perhaps that would help if it is a GPU issue. But as the other's have said, I would try exhaust software issues before thinking it is related to the hardware.

If you're getting lots of unwanted pop-ups while browsing, I would want to deal with that anyway, regardless of slowdowns, etc.

I don't get the immediate recommendation, or rather, the assumption that one has to reinstall their windows box every 6-12 months in order to keep everything smooth. Honestly, I run my Windows machine for years, and with no antivirus by, get this, not doing stupid things (and setting security settings which discourage me from doing stupid things accidentally). I've never had a problem that so borked my computer that I had to re-install. I've been bitten a couple times now and again, but nothing a little internet sluething and reg-edit couldn't fix. I pretty much only re install if I switch hard-disks, motherboard or CPU, all of which are rather rare circumstances. I usually go around 3 years between re-installs.

Premature re-installation is like burning the village to roast a pig.