Well, i formatted the PC 4 or 5 hours ago, and I havent done enough things to it in order to cause such problems.
I have installed all the critical windows updates, some drivers
(for the unidentified devices), and some programs (java, chrome, k-lite codec, tune up utilities etc).
It has only 3 things loading at startup: java update utility, catalyst control center and another thing that calls the cmd and opens a "kdbsync.exe" program or something like that (i think it has to do with the catalyst drivers).
Except from that, i had left the laptop idle for 30 minutes now, and i returned and found it working great again. I browsed the internet for 5 or 10 minutes (googling that kdbsync thingie) and the CPU went back to 100%.
I really need to find a solution to that issue soon, because I have to return the laptop tomorrow, and I still havent finished the things I have to do to it.
AddRam, I formatted the laptop's harddrive in order to do a fresh install of windows 7. After installing them and other updates/drivers/programs my described problems arose.