I didn't know anything about wubi, and I still only know what I've read up this evening. I'm not sure Mick was entirely right - wubi runs Ubuntu from within Windows using a single file in Windows as a virtual hard disk. I don't think you can install Ubuntu as a standalone system using wubi.

In which case:
I'm assuming that if I do the wubi thing through Drive C, I can put Ubuntu on Drive D through that, and then - ? - once it's on Drive D, it would be independent of Windows 7 vulnerabilities...???
is not correct. The most common problem with Ubuntu wubi installs (in my limited reading) is errors in the NTFS filesystem in the underlying Windows installation.

I'm not sure the Samsung techie is 100% right either. He's correct in that installing a second operating system may overwrite the MBR (Master Boot Record) which lives in the first few bytes of the first disk seen by the BIOS. It does this by writing a new bootloader to offer the choice between 2 operating systems. However, power users sometimes choose to write the bootloader for the second system to another location, and link it to the original MBR. (That's a very simplified explanation - don't rely on details.)

The techie could well be right that that you would lose the recovery function for use if Win7 needed to be reinstalled. (I'll show my prejudices here - that's one of the main reasons I've abandoned Microsoft. I think it's totally unacceptable to sell an operating system without a full installation disk or ISO.)

I suspect that by the time of Win7 the recovery partition may be the only way of reinstalling/repairing a dud installation. There was an acceptable halfway house - you were able to burn an installation CD from the loaded system. You could ask the techie whether this is possible with your netbook.

In summary - wubi will install Ubuntu in a file (called root.disk) within the Windows filesystem. This file may be on drive C: or D:, but that's not an installation of Ubuntu on the partition (drive). A problem with the Windows filesystem or with Windows shutdown must be rectified within Windows before Ubuntu can be booted again.

In your position, I would try a wubi install. It will give you chance to test drive Ubuntu and see if you want to make more use of it. Ubuntu installed this way may run a bit slower than a proper install, but the difference is unlikely to be significant. It's probably worth defragmenting the disks in Windows before installing Ubuntu - it will reduce the likelihood of problems and may result in improved performance.

Finally (you'll be glad to hear) if you decide you want a proper Ubuntu installation dual booting with Win7, I'm sure it can be dome. You should be able to get help on the Ubuntu forums. I know it can be dome with other flavours of linux.

And a post-final comment - if you're new to linux, don't assume you can do things the Windows way - learn the linux way. Particularly the installation of programs - don't download from the web, use the Ubuntu repositories. Programs in these are packaged with all the bits to make them run without trouble.

Phil