you will find that we rarely suggest or recommend 'optimiser' software in these forums, nor their companions, 'registry cleaners'. They often report incorrect findings and using them to make changes to a system can create problems themselves.
Of course there are specific software tools available, like MemTest for testing RAM memory, and Windows, (you don't say whether you are using Windows, a Mac, Linux, etc), has it's own diagnostic tools, like CheckDisk, (checks the hard drives for errors), and Disk Defragmenter, for defragmenting severely fragmented drives.
But if you are looking for General Maintenance, then the best utility you can use, in my opinion, is yourself. For that you can help yourself enormously by reading through Grif's A "Few" Tips for Computer Newbies. There are tons of good advice in that thread. It should keep you busy for months,
Hello. I would like to know if anyone can refer a good free pc diagnostic software? I only need it for general maintenance use, nothing heavy.