As I have mentioned in some other posts, recently I have downloaded the 1000H iso provided by Ectoplasm and Ottothecow as per this thread, and build it on a 4G SDHC with the Boot Xandros from USB for Dummies method I have posted in this thread. Everything works fine except networking.

After googling for a while tonight, I have found the solution in this Chinese blog Eee PC Hacking Blog: Install EeePC 901 iso to 900. For those who are interested, here are the instructions:
[NB. You have to do all these as "root"]

1) Download the deb packages atheros-swan-modules-2.6.21.4-eeepc_20080220-2_i386.deb and atl2-modules-2.6.21.4-eeepc_1.0.40.4-2_i386.deb from Asus update website.

2) Install them with dpkg:

dpkg -i atheros-swan-modules-2.6.21.4-eeepc_20080220-2_i386.deb
dpkg -i atl2-modules-2.6.21.4-eeepc_1.0.40.4-2_i386.deb

3) Edit these 3 files, replace all ra0 with ath0:
/usr/sbin/services.sh
/usr/sbin/wlan_on_boot.sh
/etc/alternatives/x-session-manager

4) Replace /etc/acpi/wlan.sh with the one in your original 4G or you can download the one edited by the blogger here.

5) edit /etc/modules, replace atl1e with atl2 and rt2860sta with ath_pci. Then run depmod to update module dependencies:

depmod -a 2.6.21.4-eeepc

6) Now you can reboot and run [Settings] > [Diagnostic Tools] > [System Test] > [Network test] to test your LAN and WiFi. It will prompt you to create network settings.

[NB. The blogger also mentioned problem with WPA (due to conflict between new version of xandros-wpa-supplicant and atheros wireless card) and the need to downgrade xandros-wpa-supplicant to the old version of 900 (or probably the version for 701), and use of another modified wlan.sh. But since I do not have a WPA wireless network to test it. I cannot confirm on this.]