Hi fatal exeption. Noise within the tower can only come from a few places. The fans are unlikely to be affected by your being on line. The hard drive could, but is unlikely. The internal speaker could especially if there is an irq problem. The modem speaker could. To find the source, I recommend a rolled up sheet of A4 paper. Put one end to your ear and use the other end to localise the noise source. Also check in Device Manager for conflicts, and try removing the additional memory to see if that clears the problem. What is your operating system? Windows 98 has problems managing large amounts of memory.