Downgrade fracassado para o Windows 7

(ou: a bronca do Windows 8.1 Single Language com Bing)

Num Positivo Union PCTV C1260 (BIOS 1.02 x64, EC 1.04.00), mesmo habilitando o modo Legacy, ao carregar o Windows 7 x64 SP1, me deparo com:

The BIOS in this system is not fully ACPI compliant.

Cada versão do Windows tem seus quirks, por isso não duvido que realmente seja um bug legítimo, sem o único objetivo de impedir o downgrade.

O problema é que esta máquina veio com o Windows 8.1 Single Language com Bing (link), SKU CoreConnectedSingleLanguage, que usa uma mídia diferente da comentada no post Reinstalando o Windows 8(.1) Single Language. Por enquanto, existe ISO apenas em espanhol dessa versão e demais linguagens só na base da gambiarra. Mais uma vez a Microsoft complicando nossa vida.

# lspci -nn
00:00.0 Host bridge [0600]: Intel Corporation ValleyView SSA-CUnit [8086:0f00] (rev 0e)
00:02.0 VGA compatible controller [0300]: Intel Corporation ValleyView Gen7 [8086:0f31] (rev 0e)
00:13.0 SATA controller [0106]: Intel Corporation ValleyView 6-Port SATA AHCI Controller [8086:0f23] (rev 0e)
00:14.0 USB controller [0c03]: Intel Corporation ValleyView USB xHCI Host Controller [8086:0f35] (rev 0e)
00:1a.0 Encryption controller [1080]: Intel Corporation ValleyView SEC [8086:0f18] (rev 0e)
00:1b.0 Audio device [0403]: Intel Corporation ValleyView High Definition Audio Controller [8086:0f04] (rev 0e)
00:1c.0 PCI bridge [0604]: Intel Corporation ValleyView PCI Express Root Port [8086:0f48] (rev 0e)
00:1c.1 PCI bridge [0604]: Intel Corporation ValleyView PCI Express Root Port [8086:0f4a] (rev 0e)
00:1c.2 PCI bridge [0604]: Intel Corporation ValleyView PCI Express Root Port [8086:0f4c] (rev 0e)
00:1c.3 PCI bridge [0604]: Intel Corporation ValleyView PCI Express Root Port [8086:0f4e] (rev 0e)
00:1f.0 ISA bridge [0601]: Intel Corporation ValleyView Power Control Unit [8086:0f1c] (rev 0e)
00:1f.3 SMBus [0c05]: Intel Corporation ValleyView SMBus Controller [8086:0f12] (rev 0e)
01:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8188EE Wireless Network Adapter [10ec:8179] (rev 01)
02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. Device [10ec:5289] (rev 01)
02:00.2 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 0a)

# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model  : 55
model name : Intel(R) Celeron(R) CPU  N2807  @ 1.58GHz
stepping : 8
microcode : 0x809
cpu MHz  : 498.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id  : 0
cpu cores : 2
apicid  : 0
initial apicid : 0
fpu  : yes
fpu_exception : yes
cpuid level : 11
wp  : yes
flags  : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 movbe popcnt tsc_deadline_timer rdrand lahf_lm 3dnowprefetch ida arat epb dtherm tpr_shadow vnmi flexpriority ept vpid tsc_adjust smep erms
bogomips : 3166.79
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model  : 55
model name : Intel(R) Celeron(R) CPU  N2807  @ 1.58GHz
stepping : 8
microcode : 0x809
cpu MHz  : 498.000
cache size : 1024 KB
physical id : 0
siblings : 2
core id  : 1
cpu cores : 2
apicid  : 2
initial apicid : 2
fpu  : yes
fpu_exception : yes
cpuid level : 11
wp  : yes
flags  : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 sse4_2 movbe popcnt tsc_deadline_timer rdrand lahf_lm 3dnowprefetch ida arat epb dtherm tpr_shadow vnmi flexpriority ept vpid tsc_adjust smep erms
bogomips : 3166.79
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management: