Malware is just a module that is tied to and run via Trojan. Trojan and Malware are actually worlds apart in terms of complexity and application and most malware just looks like unallocated space on the disk (when things are done the right way) and is run via circumvention of execution protocols i.e Trojans, however Malware still has to preform tasks using standard system protocols meaning Malware has to run just like any other ordinary software does. And how does it do? Well, the answer is simple via Trojan and also what I'm getting here at is that becasue in order for Trojan to be able to preform tasks as regular software Trojan is going to have to need an ability to write to the disk and insurance that it won't get overwritten over time and the only way it can achieve this is by getting "registered (Malware doesn't have to be entered into the registry to operate, though) " with the OS usually as a system task and then and only then "Virus" can get resources allocated to it so that it can be used to run all sorts of other programs thus it can be located quite easily. And since it is a must for Trojan software to be recognized as a system process by any given OS then in turn its location on the disk will be known to the OS in question and this is the exploit antiviruses use or in other simpler words they (anti-viruses) locate where the core data of Trojan is stored on the disk and then they( antiviruses) overwrite(delete) Trojan and all modules associated with it.
Well, yeah Malware can be a bit pesky when it comes to locating it on the disk, but Trojan is very easy to locate and delete and you can't run Malware without Trojan (unless you installed it using Trojan and it is recognized by the OS) and that's why nobody really cares about deleting Malware
