I read it somewhere on this forum that the effects of malware did not go even after REINSTALLING the OS.

2. Isn,t formatting supposed to CLEAN the partition DRY??

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If you remove the partitions and reformat, there is nothing that can survive that.

XP can be reinstalled "over the top" of itself to correct corrupted files, but that may not get rid of malware.

Give a man a fish and you feed him for a day;
Teach a man to fish and you feed him for a lifetime;
Then industry pollutes the water and kills all the fish.

I beg to disagree...
format c only removes the majority of the info on the hard drive.. format u gets rid of it ALL. There are certain parts of a HD that are skipped in a regular format ( on purpose)

Also, harmful commands can be stored in DMI and can only be cleaned by a security expert who knows the bios commands.

Also...
certain malware and bad commands can be stored in RAM and can only be cleaned by a cleaning the bios immediatly after pulling the RAM for a few minutes ( and re installing)and then flashing the bios.
This is not conjecture it is fact. Little known fact but true facts none the less.
I once had a PC come in that reloaded the same problem files after writing the drive to zeros, it was discoved that the DMI and bios commands kept in the RAM was reloading the bad commands that told windows setup to set up all the same connections ( hidden) for link up support.
No guff.

A computer is a perfectionist's nightmare.