Hi. This is my last report on my observation. For poeple who might be interested, I will list my computer's configuration below.
After I made sure everything was working and McAfee did not find any malware, I reconnected my Snow Leopard drive. Guess what has happened? Yes, the black screen of death (BSD). It should be noted that the Snow Leopard requires AHCI setting. From what I obsereved, Windows OSes, when two (or possibliy more) versions are installed on the same drive, driver installation for an additional drive has to be done twice, first without AHCI enabled and then, after rebooting, with AHCI enabled. Interestingly, Vista (see configuration below) booted OK first time after AHCI was set but did not boot (went into BSD) at the second booting. In contrast, Win 7 went int BSD on the first boot. Since I knew what was causing BSD in my case, I did not have real problem in fixing them.
My computer's configuration:
Mobo: GA-EP45-UD3L
CPU: Intel E8500 at 3.8 GHz
RAM: 6 GB of 1066 MHZ at 860 MHz
Monitor: Acer 24 in HDMI HDTV (1920x1080p)
Video: 9800GT with 512 MB DDR3
4 drives, all SATA, IDE mode: one has Vista Home Premium 32 bit in partition 1 (active) and Win7 pro 64 bit in partion 2; drive 2 has Win 7 Ult 64 bit built 7100; drive 3 is used for data and system backups; drive 4 carries Mac OS X
Win 7 evaluation copy never gave problem indicating that, in my case, the BSD occurred only OSes on dual boot drive.