Usually, the n that ended before letters like b, p, m and few others, the n became m. For example, senpai where sometimes it becomes as sempai.

For pasokom, the original word is personal computer then becomes persocom (in English way). When persocom became Japanization, it becomes pasokon but persocom ended with an M. So, pasokon becomes pasokom.

How about CAPCOM? Dont you think that they supposed to say it as Kapukom? Sounds funny.