BUG #6429: i cannot complete installation due to a forgotten password

The following bug has been logged on the website:

Bug reference: 6429
Logged by: seph
Email address: sephaliii(at)hotmail(dot)com
PostgreSQL version: 9.1.2
Operating system: Windows 7
Description:

i have reached till the point of inserting the password and retyping it for
verification during the installation. (I had never installed postgresql on
this machine before.)When i pressed next to proceed i got this error
message: "The password specified was incorrect. Please enter the correct
password for the postgres windows user account."
On finding this i re tried the same password to no avail. I am the only one
to use this machine.
I uninstalled postgresql via control panel and deleted the whole folder
where i allowed postgres to be installed(along with it's data folder). Then
i downloaded it again, ran the installation, provided the very same
password, clicked next and again i got the error message stated above. I
googled the problem and found that the problem is related to the service
account.
i searched for that account but could not find it.
i tried a code in the command prompt window ( NET USER <username> /
DELETE)that was suggested by postgresql.org, but it said that the account
was not found. Hence, i still cannot install postgres. I even tried creating
a new user account on windows and downloaded postgresql there and ran the
installation but it still failed.
I should add that i deleted the whole POSTGRESQL folder from my computer and
expected every trace of it to be gone but since no new password is being
accepted the original service account must still be somewhere.
I want to either delete the service account or retrieve the password that
should allow me to install.

I am a student and really need postgresql for a module.
Please support team, respond as soon as possible since i have a test coming
on 8th February.
Yours, seph