我认为你将被迫做一个重新安装，你 * 可能 * 运气与修复选项。
如果您将不得不走这条路，重新安装，我一定会删除所有剩余的文件从主数据库和临时数据库只是为了安全起见。
如需了解更多信息：MSDN Uninstall
我还想借此机会评估一下您的备份策略，并为您的SQL Server对象实施源代码控制，如果您目前还没有这样做的话。

如果您有master、model和msdb的副本，并且可以还原它们，则您将拥有所需的内容。您可能不必重新安装二进制文件（如您所述）。如果没有这些备份，您将必须重新安装SQL Server。
https://msdn.microsoft.com/en-us/library/ms190679.aspx

Putting my answer here years later, but it might help somebody else.

!!! Before attempting any of the below, make sure:
!!! -- either make a clone of the VM in question, work from that
!!! -- if no clone possible: backup your databases and its procedures etc. 

As a first option/bet, selecting a System recovery point from 
within Windows might be the way.
(On any Windows you get to work with, check/enable System Recovery as 
the first step!)

A second way might be to have a dedicated 3rd party uninstaller clean 
up MSSQL (and all the other MSSQL programs?) *completely*, 
before doing a reinstall.
If you have an incompleted uninstall like I do (see below), you could
do a reinstall, and remove the new instance with the dedicated 3rd 
party installer.

A third way might be to locate the install directory and wipe that
completely, then clean up the registry with a registry cleaner.

My case (2021, Win10, MSSQL 2019 dev edition):
I messed up my MSSQL by creating a second user with the same name/pass
within MSSQL, but with no rights yet. In effect, I overwrote/reset 
my admin account to have zero rights. Pretty dumb (and MSSQL should
have warned/refused).
Neither a reinstall of MSSQL(,SSMS) MSSQL wipes the user(!?).