Asa tech savvy person and all-time traveller I recently acquired a mobile network data flat of one of the local German and international providers - the one with pink logo. For every contract/subscription you sign, you usually get some perks, extra stuff, a mobile handset or - in my case - one of those netbooks. The Acer Aspire One 531 I was sent does feature an integrated 3G modem by OPTION Wireless ad comes with Windows XP Hometo my demise. Failing in preparing a proper backup (Acer gives you a backup software to burn media - but a netbook does not have an optical drive, and maping the DVD burner in my home Vista machine is not acceptable use of the software - and thus deactivated) I killed XP home anyway and installed Win 7 fresh of a 8 GB USB flash (see here for a geek howto, or here for the DAU help with prepping the USB stick). All worked well - even a complete Office 2007 and Visio2007 found its way on the device - no driver problems, except... for the 3G!
I spent way too much time to figure this out, so here are the resources needed: Driver handling & tweaking plus driver links http://www.itgrl.de/2009/03/31/aspire-one-3g-treiber-fur-umts-modem/ Driver Links Acer http://global-download.acer.com/GDFiles/Driver/3G/3G_Option_5.0.12.0_XPx86_A.zip?acerid=633776034442008284&Step1=Netbook&Step2=Aspire One&Step3=AO531h&OS=X01&LC=de&SC=EMEA_8 Driver Links Option (IMEI required!) http://www.option.com/en/support/software-download/product-list/
After trying desperately to use the T-Mobile web'n'walk software for a while (even the EMBEDDED Version taken from the mysterious FTP server in Czech Republic) did always UNINSTALL the Option drivers leaving my netbook without connectivity. Using the ACER Software DOES the trick though, but yu have to tweak it: the Acer 3G Connection wil fail to connect (it finds the device, SIM is entered, network is acquired) but the it get stucks while "connecting" aka "Verbinden...". Again, calling the friendly mobile provider support, we quickly analyzed that we are only one step away. Simple solution: create a new modem connection with *99# as the number to be dialed and all works well suddenly!
Now, back to real work... message me if you have a working setup with w'n'w software on Win 7 and internal Option MOx40 cards... or actual stand alone drivers for Win 7 that are NOT deleted when installing w'n'w :-)