Goodness sakes what kind of computer was it? Old new or what. If it was old it was probably time for the computer to kick the bucket. I dont see how just messing with ram can cause smoking. If the ram was put in backwards or incorrectly it may have jammed the socket, if so then the electricity going into the ram slot maybe over loading due to damaged power receptor pins. This circuit overload could cause the rest of the system over load and cause things such a hard drives cd drives especially the power supply to malfunction and cause the system to smoke.
Desktop: P4 2.8Ghz HT/ 512mb ram /, ATI Radeon X300 SE 128mb
Laptop: AMD Athlon 4 1200+/ 512mb ram/ Cyber blade Xp vid card.