amilo m3438g

please can someone help me, i have an amilo m3438g laptop, recently had a load of spyware , malware , backdoor trojans etc, and think now i have got rid of them, but now i have re-installed windows about 3 times, but yet the laptop runs like a bag of poo,(sssllllllllooooooowwwwwwww).
can someone help please...