Linux should allow you to remove everything you want. (Carefull)
Don't use disk druid or any graphical thing. You must request to use fdisk directly to make sure you have all the functionality.
On most instalations you can switch to a text console where you can use the normal tools. So if you can't find a button for normal fdisk you might need to do that.
Start the installation on the step before partitioning (don't know exactly which one that is) switch to a text console. (Try Ctrl-Alt-F1 to Ctrl-Alt-F4, the one that gives you a shell (probably with a # prompt) is the one you want). Use fdisk on your harddrive (probably hda) ... "fdisk /dev/hda" and remove the partitions you don't want.
You might need to take a look at the commands for fdisk first. "m" will print help, "p" will print the partition table and, as expected, "d" will delete a partition. Use "w" at the end to write and exit. Then reboot your machine.
A word of caution, make sure you have the right active partition (in your case probably hda1).
Good luck
cl