Surchauffe sous kubuntu

Bonjour,

Je reviens de quelques tests sur l'ordinateur de ma copine, qui tourne sous kubuntu 9.10 ( la 10.04 est encore trop instable )

Il subit un sérieux problème de chauffe:

straw@Fanny:~$ acpi -t
Thermal 0: ok, 71.0 degrees C
Thermal 1: ok, 71.0 degrees C

( test avec une seule vidéo youtube sur batterie )

J'ai aussi fait un test en charge
straw@Fanny:~$ acpi -t
Thermal 0: ok, 89.0 degrees C
Thermal 1: ok, 89.0 degrees C

J'ai déjà réglé le processeur en powersave, baissé la luminosité d'écran au minimum, mais rien n'y fait, le PC chauffe toujours autant...

Quelqu'un aurait une solution SVP?

Ps: un dernier test, terminal et commentçamarche allumés, sur batterie:
straw@Fanny:~$ acpi -t
Thermal 0: ok, 59.0 degrees C
Thermal 1: ok, 59.0 degrees C

[EDIT] Voilà quelques détails supplémentaires:
straw@Fanny:~$ lspci
00:00.0 RAM memory: nVidia Corporation MCP78S [GeForce 8200] Memory Controller (rev a2)
00:01.0 ISA bridge: nVidia Corporation Device 075e (rev a2)
00:01.1 SMBus: nVidia Corporation MCP78S [GeForce 8200] SMBus (rev a1)
00:01.3 Co-processor: nVidia Corporation MCP78S [GeForce 8200] Co-Processor (rev a2)
00:01.4 RAM memory: nVidia Corporation MCP78S [GeForce 8200] Memory Controller (rev a1)
00:02.0 USB Controller: nVidia Corporation MCP78S [GeForce 8200] OHCI USB 1.1 Controller (rev a1)
00:02.1 USB Controller: nVidia Corporation MCP78S [GeForce 8200] EHCI USB 2.0 Controller (rev a1)
00:04.0 USB Controller: nVidia Corporation MCP78S [GeForce 8200] OHCI USB 1.1 Controller (rev a1)
00:04.1 USB Controller: nVidia Corporation MCP78S [GeForce 8200] EHCI USB 2.0 Controller (rev a1)
00:06.0 IDE interface: nVidia Corporation MCP78S [GeForce 8200] IDE (rev a1)
00:07.0 Audio device: nVidia Corporation MCP72XE/MCP72P/MCP78U/MCP78S High Definition Audio (rev a1)
00:08.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Bridge (rev a1)
00:09.0 IDE interface: nVidia Corporation MCP78S [GeForce 8200] SATA Controller (non-AHCI mode) (rev a2)
00:0a.0 Ethernet controller: nVidia Corporation MCP77 Ethernet (rev a2)
00:0b.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Express Bridge (rev a1)
00:14.0 PCI bridge: nVidia Corporation MCP78S [GeForce 8200] PCI Bridge (rev a1)
00:18.0 Host bridge: Advanced Micro Devices [AMD] Mobile K10 [Turion X2, Athlon X2, Sempron] HyperTransport Configuration (rev 40)
00:18.1 Host bridge: Advanced Micro Devices [AMD] Family 11h [Turion X2, Athlon X2, Sempron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] Mobile K10 [Turion X2, Athlon X2, Sempron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] Mobile K10 [Turion X2, Athlon X2, Sempron] Miscellaneous Control
00:18.4 Host bridge: Advanced Micro Devices [AMD] Mobile K10 [Turion X2, Athlon X2, Sempron] Link Control
02:00.0 VGA compatible controller: nVidia Corporation C77 [GeForce 8200M G] (rev a2)
07:00.0 Ethernet controller: Atheros Communications Inc. AR5001 Wireless Network Adapter (rev 01)