If there is a remnant of the old partition table left then it's easy to get rid of it. Just run a dd like so:
dd if=/dev/random of=/dev/sda bs=1 count=512
Only run this if you are sure you want to erase all partitions and start over. "sda" is the harddrive you're working with.
If you do this you will have to reinstall Windows 7 again. I'd recommend creating the partitions with the Ubuntu Live CD, that way the Windows installer doesn't create the 100MB System Partiton anymore, and you can be sure that the partitions are actually there. Good luck.
First, there's no such thing as a "partition... which is... unallocated space." A partition is, by definition, allocated space. If you deleted or shrank a partition, the result is unallocated space. Although I believe I understand your meaning in this case, miscommunication on this score can lead to a lot of wasted effort as two parties communicate at cross purposes.
Second, although it's OK to shrink partitions in Windows in preparation for installing Linux, you should never create a partition using the Windows tools with the intention of using it in Linux. Doing so may work if you're lucky, but if you're not lucky, Windows will implement its proprietary Logical Disk Manager (LDM) system, and you'll have to jump through hoops to undo this change before you can install Linux. I don't believe this accounts for your problem, but it bears mentioning.
My suspicion is that you're using an older Master Boot Record (MBR) partitioning scheme and have run into a partition table difficulty. There are several things that can cause this type of problem. Many of them can be fixed with my FixParts program. See its documentation, and this page I've written on the topic. If you still have problems, post back with more detail, such as the output of the following commands, typed in a Linux terminal from an emergency disc:
fdisk -l /dev/sda
parted /dev/sda print
gdisk -l /dev/sda
If you use Ubuntu, precede each of those commands by
sudo; with other emergency discs or distributions, be sure you log in as
root. (Logging in as
root is standard with most Linux emergency discs.) If you use Ubuntu, you'll probably have to install
gdisk by typing
sudo apt-get install gdisk, too. Edit your original question to include the output of these commands.
Ubuntu does not support Windows-specific "dynamic" disks. This may be one reason for partitions not showing up on installing Ubuntu or when partitioning a drive from Ubuntu.
Obviously this can only be done from Windows (see Window Server Support and Microsoft Technet), e.g. with a partitioning tool (e.g. AOMEI Partition Assistant).