Perhaps your computer is running low on power? I don't think bad sectors will do that. Or at worst your HD may be failing.
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Necrosaro: Windows XP Pro x64 Edition SP2 | Intel Core 2 Duo E8400 3.00GHz, 1333MHz FSB, 6MB L2 Cache | Asus P5Q Deluxe, Intel P45 Chipset, Socket 775 | 4GB Kingston PC5300 DDR2 | Nvidia GeForce 8800GT, 1024MB | Creative SB X-Fi Fatality Edition | Western Digital Raptor WD1500ADFD, 150Gb, SATA, Western Digital WD5000AAKS, 500GB, SATA | LG 16x DVD-RWx2 SATA.