Just a heads up, I noticed that when booting up an Asus netbook you want to hit ESC to pull up the menu to choose what media to boot from. If you have Bootbooster enabled, you may need to disable it in the bios to access the menu. In fact, Bootbooster makes it difficult to get to the bios, since it gets through the initial bios startup so quickly. You just have to tap that F2 repeatedly as the system is coming up, in my experience.
In any case, it seems to me that when you deleted your Ubuntu partition, you deleted the portion of the Grub bootloader that's on the Ubuntu partition. (Grub is the menu that gives you the option to boot to Windows or Linux.) You can read more about it and how you might go about fixing it here:
Another solution is to just install the next Linux distribution you plan on replacing Ubuntu netbook edition with. Most of the time they install a bootloader, which would replace the corrupted one you have now and allow you to boot properly again.
And now a bit of theory that may help you understand:
A bootloader is a tiny program that is installed at the start of your hard drive, in the Master Boot Record. When you boot up your computer, it first checks this section for instructions on where to proceed next. The bootloader installed here is very simplistic, pointing to another location on the hard drive where the next stage of the bootloader can be found. Once this next stage is executed, you get the fancy stuff drawn to the screen giving you a choice of which partition to boot to.
The Windows bootloader assumes that you want to boot to Windows only, so it points directly to the Windows startup.
Linux bootloaders, like Grub and Lilo, point to a more complex program that gives you a choice of which OS to boot to.
When you installed Ubuntu, Grub replaced the Windows bootloader in the MBR.
When you deleted your Ubuntu partition, the initial stage of Grub pointed to nothing, making it unable to find the next instructions to boot to.
What you will do to fix this is replace that remnant of Grub with the Windows bootloader so that it just points to windows again.
Alternately, you would install another version of Grub that points to a fresh Linux install for the next stage.
Probably unnecessary info, but it's good to know.
Hopefully I understood the gist of your problem properly.