Welcome, Igor.
Since OpenBSD is already installed, you only need two things to re-install:
- The 4.9-release RAMDISK kernel, bsd.rd.
- The installation filesets and kernels, via network or pre-fetched media.
The RAMDISK kernel may already be on the system; it is installed by default by the installation scripts. Look in the root directory, if you find the file "bsd.rd" you have it. If not, you can obtain it from your nearest mirror in /pub/OpenBSD/4.9/i386 and store it in the root directory.
The installation filesets (.tgz files) and kernels (bsd*) are also in that directory. If the Alix system cannot reach the Internet, these can be preloaded onto a USB stick (in FAT format) and used during re-install.
To boot the RAMDISK kernel, if it is in the root directory, all you need do is reboot the ALIX system. At the boot> prompt, type
bsd.rd and press Enter. After this kernel boots, you will be prompted to Install, Update, or drop to the Shell.
If you do not have an Internet connection, insert your USB stick with the pre-fetched filesets and kernels after booting, but before running the install script. The kernel will assign the stick to a pseudo SCSI drive, sd0 or sd1 or some other number, and you will see this assignment on the console. If there is only a single MBR partition on the stick, inform the install script to find the filesets on disk, on that device, then in the "i" partition.
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To configure your netstick for dialing an ISP, please see wlm2's thread from August where we gave information on configuration. We pointed wlm2 to two man pages, one of which had several PPP configuration examples, and we pointed wlm2 to a section of the OpenBSD FAQ on configuring PPP.