So I purchase a spiffy new WD HDD, pop it in without a second thought, and it works. Yay! I remove it sometime later to bring to a friend's house (properly packaged in ant-static and all that) bring it back, pop it in, and my PC no longer starts up successfully. BIOS init. is incredibally slow, going so far as to pause before drawing the last character of the phrase "Memory Check" during startup. After a very slow memory check (even though quick tests are enabled), the rest of it is displayed 1/4 of the screen at a time, diagonally.
I grow quite worried as the system just stops after performing the HDD SMART test (which passes, amusingly enough) turn it off, and pop the drive. After examination, my ATA133 (thin, yellow) cable has two connectors: black and grey. I try the opposite position, no effect. I switch the HD from primary master to slave, no luck. I move it to CS (Cable Select, I believe) and all is well - it identifies as Primay Slave, but it's bootable. I boot into Gentoo Linux 2004.2 (2.6.7-gentoo-r10 kernel with all the bells and whistles) (I also have Slackware installed) and discover the fsck app complaining about a lack of DMA.
So, I whip out my handy hdparm app and have a look - true enough, DMA is disabled. I attempt to enable dma (-d1) and it fails with "operation not permitted". Any ideas?