Stuck in GRUB after Windows install - only Grub> prompt, nothing else - how to proceed?

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http://askubuntu.com – Hi Ask Ubuntu Support Team, I get stuck in a black GRUB screen. I want to learn about Ubunto on my Win7 laptop. I use wubi.exe and follow the steps of the "Installing Ubuntu with the Windows installer" guide. I use my old laptop DELL LATITUDE D810 with a 300GB HD with two partitions C: Win7 system disk (Ntfs, 38.5 GB free out of 78.1 GB) D: Data disk (Ntfs, 131 GB free out of 219 GB) Because of the available free disk space on data disk D:, in step 3 of the guide, I select disk D: as target for a 30GB Ubuntu installation. This selection is accepted. The installation completes to step6 wher (HowTos)