I currently have 128mb of sdram in my pc and i wanted to upgrade it but all i got is pc100 (theres pc133 in my comp) so i was wondering if mixing pc100 and pc133 can be done without making the motherboard melt down

forget it i've solved the problem myself. If my motherboard supports both pc100 and pc133 it will works, otherwise, it will either shows a wrong ammount of ram or it won't start up.