1. One machine has existing windows. It had ubuntu 8.04 . I deleted the partition so I could install ubuntu 9.10 . Now the machine refuses to recognise usb stick, usb CDROM so I cannt even boot from them.
Boot from the windows CD using the conventional optical drive and enter recovery console. type "fixboot /mbr". Reboot.
2. Other laptop : i thought I will not touch the system that is working fine( ubuntu 9.04) So I used USB CDROM and ubuntu 9.10 disc on it to create a usb stick for 9.10. I did boot from USB CD and chose the stick to install and chose not to install grub as I wanted only one OS on the stick and thought grub will be redundant. (While installing it had asked location of grub on HD(0) etc and that was not relevant . I thought). So I happily ended the process disconnected USB CD ROM drive and restarted the laptop and again I got the sacry 'grub rescue >' prompt
Boot from Ubuntu, enter rescue mode, type grub-install /dev/hda (or sda or XXX depending on your partition layout.)
Regards, NMK.