hello,
i installed RouterOS on my USB Flash Drive today from the windows xp machine. then i inserted it in the same machine and it did boot perfectly as the primary device from the BIOS.
all this was great.
but now after removing the USB and restarting the xp machine it is giving me error
" NON SYSTEM DISK OR DISK ERROR REPLACE AND STRIKE ANY KEY WHEN READY "
after this i tried out the USB on a Win7 machine and after rebooting Win7 is not loading now.
-sid
Of course, the USB contains the RouterOS installer, if you boot from that USB disk, it will start RouterOS installation and rewrite the MBR and Format the disk.
Do NOT boot from this USB disk on some windows machines 
how do i recover my data from the HDD now?? or can i rewrite the MBR??
you need some MBR recovery tool, you can google for it
i tried that but it has marked the HDD as UNPARTITIONED SPACE.
how to solve that.
damn scary!!! help will be highly appreciated.
No idea, data recovery not my specialty
Software Ontrack EasyRecovery Pro or specialized Data Recovery Service.
Regards, Grzegorz.