If you are having problems, the most likely problem would be the cracked program contained some sort of Trojan. Or the website your brother downloaded it from, unless he used Firefox or opera to view this website, then it most likely had some sort of ActiveX drive by download malware hidden in its pages.
Therefore the best thing I would recommend first of all is to do a full system scan with a high quality Antivirus which is good on finding Trojans. Such as Kaspersky Anti virus is the best. (note: Norton is very poor on detecting Trojans so if this is what you have you will need to use a separate trojan program like Ewido).
Then after this do a scan with Microsoft antispyware. Then finally do a junk file and reg clean with Ccleaner.
This should remove whatever malware the software may have installed.
Finally if you are having random reboots then have you looked in your Administrative event viewer inside your Control Panal to look at the error code given each time the PC reboots?.