Have you kept an eye on the ram and cpu as your programs are running? is it possible you have a memory leak eating all of your memory up ? Bar that it could be anything, virus, hardware change, just do the usual scans and such ! - a favorite of mine is ccleaner ;)
The CPU and the Ram are not the problem. And it's not a memory leak from what I see as my free Ram is almost the same as when I start up my PC (under 50% used Ram). I'll try CCleaner now. Thanks for the advice.
Do you keep your operating system up-to-date? Do you have virus/malware protection that's up-to-date and run on a regular basis? Have you recently changed any hardware?
I haven't changed any hardware. I have win7 and it's up to date. I really didn't install an anti-virus program 
but I try to download safe things, so only Win Defender on this side and it didn't detect anything.
For the themes I used universal theme patcher.
The problem looks really like a memory leak issue because the longer the PC is on, the slower it starts up some things - though the Ram stays the same so it can't be a mem leak. And it's kind of odd how only some things start really slowly - I'm basically waiting for some trivial thing like properties to show up. I thought it might be an HDD issue but the HDD seems to work fine (normal copy speed).
And it's not like I am compiling something great - just an exercise:
#include <iostream>
using namespace std;
class Date
{
private:
int day, month, year;
public:
Date(int inputDay, int inputMonth, int inputYear)
:day(inputDay), month(inputMonth), year(inputYear){}
Date& operator ++ ()
{
++day;
return *this;
}
Date& operator -- ()
{
--day;
return *this;
}
void displayDate()
{
cout << day << " / " << month << " / " << year << endl;
return;
}
};
int main()
{
Date myDate(25, 7, 2013);
myDate.displayDate();
++myDate;
myDate.displayDate();
cin.ignore();
return 0;
}
Now, just after I started my PC it needed 1s to compile. Yesterday just before I shut down my PC it needed like 30s to compile and it stopped with great delay at every possible point.
Should I defrag my HDD(I don't see how this will help), should I check it for errors? Do you have any idea what might be causing this?
Thanks a lot guys, I really appreciate your help 
