|I'm assuming you're telling the truth and it was you that changed your own account to have limited privileges. If it wasn't you, someone thought they had a reason for doing that.|
Users of XP and 2000 have administrator privileges by default.
Any user that has administrator privileges can change your user account from having limited privileges to having administrator privileges,
with the exception that they can't change the built in Guest account to have administrator privileges (if the Guest account has been enabled by someone with administrator privileges).
If all other users that have those administrator privileges have passwords, if you don't know the password for any user that does, ask them if they will change that for you.
When you boot the computer into Safe mode, the built in Administrator user account has no password for it by default. If that situation hasn't been changed, you can load the Administrator user (select it and just press Enter) and change the limited privileges of your user to have administrator privileges.
No two users can have the exact same number of the same characters in the same order in their user name.
There can only be one user that is spelled exactly Administrator.
(It's probably not case sensitive, as in, it probably doesn't matter which letters are upper or lower case.)
The built in Administrator account is normally only available to be selected in Safe mode.
It can be deleted by another user with administrator privileges in Safe mode, if at least one other user has administrator privileges when you boot normally. That's the only way you can have a user spelled exactly Administrator when you boot normally.
"I am using windows XP SP2"
You should be using XP SP3.
Most if not all new and recent and fairly recent Windows updates, and many add on Microsoft programs, will not install unless SP3 updates have been installed.
"I get SQLUDB error and when I disconnect
my connection through the modem continuous prompt appears showing DB2 error."
That may or may not have anything to do with your user having limited privileges.
If that problem does not go away when you have administrator privileges, I have no idea what to do about those errors - I know nothing about mysql and IBM-DB2 - perhaps someone else can help with that.