Hello ng, I was wondering if anyone could help me fix a new problem that`s come up. While my computer is on, there is a noise coming from it... I usually have problems like that, which are almost impossible to explain to others and therefore hard to fix. I`ll give it my best shot. Lasting for a total of 8 seconds, I hear a sort of resonance which builds in strength gradually, then drops. A new period of 8 seconds starts, again building up from zero to annoyingly audible. I have spent a lot of money making my computer ultra-silent, so the effect is pretty bad. The sound seems to have no relation with the amount of work load I put my computer through. It makes no difference whether the computer is idle or doing heavy encoding duties or something. When booting the noise is really quite loud and constant for a couple of seconds, soon afterwards the cycles starts. There is no difference whether the computer has been off for a few seconds or a few hours. Recently, there have been 2 computer related changes. First, I switched from cable internet access to ADSL internet access. This can hardly affect my system, as the modem was connected in both cases to my router and it couldn`t care less where the connection is coming from. My second change has been replacing a P-ATA 30 GB IBM Deskstar GXP75 harddisk with a P-ATA Hitachi 7K250 250 GB harddisk. Other than these two changes, nothing has changed. The problem came up `suddenly`. And it won`t go away. Due to the position my computer is in (it is hard to reach), it is really difficult to have my computer running and physically checking what`s going on. However, if I were to judge where the sound is coming from, I would say it`s coming from the upper part of the tower. The most likely suspect is therefore my power supply. I`m running an ultra-quiet Lexus power supply, 300 watt. It is less than a year old. Perhaps it cannot supply enough power to the system or something, so I would like to determine the power requirements of my system. Can anyone tell me how I could make an educated guess in this matter? Or, look at my specs and take a guess yourself. Case: AOpen Miditower ATX HQ45AP Power supply: Nexus NX-3000 (replaced the AOpen power supply) 300 watt Motherboard: MSI K7T Turbo 2 Limited Edition Processor: AMD Athlon XP 1800+ Proc.Cooler: not certain, I think it`s the Nexus KCZ-2700 LS Harddisk 1: Seagate Barricuda 7200.7 80 GB (ST380011A) Harddisk 2: Hitachi 7K250 250 GB DVD-ROM: Toshiba SD-M1802 16x CD-RW: Lite-on LTR-52246S 52x 24x 52x Diskdrive: Sony 3,5" Diskdrive 1.44Mb Graphics card: 3D Blaster 4 Titanium 4400 (nVidia GeForce4 4400 128 MB) (REMARK: took off the noisy power supply, replaced by Zalman ZM80C-HP heatpipe passive cooling solution) Memory: 768 MB SDRAM Soundcard: Terratex DMX X-Fire 1024 4.1 Controller card: USB 2.0 Speakers: Creative PCWorks FourPointSurround 1500 Network card: Sitecom PCI Fast Ethernet card 10/100 Mbit Router: Sitecom DC-202 Trackball: Logitech Marble Mouse USB Mouse: Logitech Cordless Mouseman Wheel USB Tablet: Wacom Graphire 1 USB Keyboard: Logitech Internet Keyboard (serial) Scanner: Canon CanoScan N670U USB Printer: HP DeskJet 720C LPT2 CRT monitor: Iiyama Diamondtron A705MT Vision Master Pro411 17" TFT monitor: Dell 1504FP 15" I`ve included all peripherals which are powered on when using the system. I welcome any suggestions! Regards, Willem