The graphic card is a Silicon Integrated Systems [SiS] 771/671 PCIE VGA Display Adapter (rev 10) doesn't work with the sis driver provided by Mandriva.
During installation choose the generic VESA driver, and set the resolution to 1280x768 (the VESA driver doesn't support 1280x800)

After the installation download this drivers (only 2d acceleration): https://www.sakya.it/linux/sis_drivers.tar.bz2
Source of this drivers can be downloaded here: https://www.sakya.it/linux/sis_drivers_src.tar.bz2
Execute these commands:

mkdir sis_drivers
cd sis_drivers
tar -xf ../sis_drivers.tar.bz2
su 
[insert root password when asked]
cp -f  usr/lib/xorg/modules/drivers/sis_drv.* /usr/lib/xorg/modules/drivers/
cd..
rm -rf sis_drivers
exit

Now edit the xorg.conf with these commands:

su
[insert root password when asked]
kwrite /etc/X11/xorg.conf

Modify the sections "Monitor", "Device" and "Screen" this way:

Section "Monitor"
    Identifier "monitor1"
    HorizSync 31.5-90
    VertRefresh 60
    
    # 1280x768 @ 60.00 Hz (GTF) hsync: 47.70 kHz; pclk: 80.14 MHz
    Modeline "1280x768_60.00"  80.14  1280 1344 1480 1680  768 769 772 795  -HSync +Vsync
    
    # 1280x800 @ 60.00 Hz (GTF) hsync: 49.68 kHz; pclk: 83.46 MHz
    Modeline "1280x800_60.00"  83.46  1280 1344 1480 1680  800 801 804 828  -HSync +Vsync
    DisplaySize 330 210
EndSection

Section "Device"
    Identifier "device1"
    Vendorname "SiS"
    Driver "sis"
    Screen 0
    Busid "PCI:1:0:0"
    Option "DPMS"
    Option "XvDefaultAdaptor" "Blitter"
    Option "EnableSiSCtrl" "yes"
EndSection

Section "Screen"
    Identifier "screen1"
    Device "device1"
    Monitor "monitor1"
    DefaultColorDepth 24
    
    Subsection "Display"
        Depth 24
        Modes "1280x800" "1280x768" "800x480"
    EndSubsection
EndSection

Now reboot the X server (press CTRL-ALT-BACKSPACE) and the screen resolution should be 1280X800.

No luck with the softModem (a Motorola SM56).
I tried with the Motorola driver, but the modem doesn't work at all.

The Atheros Communications, Inc. AR5006EG 802.11 b/g Wireless PCI Express Adapter (rev 01) works great with ndiswrapper and the Windows XP drivers.
Download the Windows XP drivers from here:
https://www.sakya.it/linux/FSC_WN2302AmPCIWLANIEEE80211bg_V53056_1014542.ZIP

Unzip the archive and when Mandriva asks for a driver, choose ndiswrapper (and not the ath_* Madwifi driver) e choose the inf from the Windows XP driver.