"Default" User Account deleted

I have somehow deleted the Default User Account from my PC.
I am the only user of a standalone PC running Vista Home Premium. My account
is as Administrator. I have turned off UAC

Some weeks ago, in an effort to preserve disc space I deleted directories &
files that I felt I would not need, such as Users\Public. I have somehow
during this process managed to delete the "Default" user account.
At the same time (and on several occasions since), I deleted all but the
latest Restore Point (using Disc Cleanup). Therefore I cannot go back to
before.

As a result I can not create a new Account, nor use the guest account. If I
create a new one or try to activate the Guest account, neither show in the
C:\Users subdirectory, and they are not recognised by User Account Profile
Service.

I do not have the original install discs for Vista (PC came pre-configured
from OEM, with install files hidden away somewhere inaccessible on the hard
drive), and there is no option for a REpair Install, only a new Clean
Install, which would involve backing up / reinstalling / restoring all
programs and files.

Does anybody know of a better way to reinstate the "Default User" and / or
Guest Accounts ?