I would've thought that depending on the Windows CD you are waiting to receive by post, get the "boot disk" with regards to that particular window straight from Microsoft's website.
I recently needed Windows XP Pro. boot disk, in order to boot my system & I simply typed in "Windows XP Professional boot disk" in Google & the first link took me to Microsoft's page. Here, you download the boot disk program, which is around 4.25 MB (for Windows XP Pro.) & then run it, which will take you to Command Prompt & will ask you to insert floppy disk one after the other, in order to make boot disk, needing around 6 formatted floppy disk.
Now, assuming that you can't use your window, you need to do the above process on someone else's computer & once you made the boot/startup floppy disk, you can use it on you PC, starting from restarting your PC, while leaving "Disk No. 1" in the floppy drive & then the message will ask you to insert the next floppy disk & so on.
Since I booted & formatted my hard-drive through bootable Windows XP Pro. CD, I can't be too sure, how far these floppy disks will take you, but I would've thought that, you should come across a "hard-drive formatting" option (along with any partition, if you fancy doing so), appearing right at the end of the boot process.
Just give it a go, since you've NO data to lose & if you make a mistake, then I suppose............... you'll for sure, LEARN from that mistake