Deleted the *Default* REG_SZ key in ProfileList and more problems!

Hello Everyone!
As you seen on my Thread title, I deleted a key called Default NOT the key with the parentheses where it is located in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList and didn't create a backup! I deleted it because I got a user name in my login screen called *Other User* and I didn't CREATE IT AT ALL! So I searched and I found this How to make Windows 7 show user list on login screen, not just the - Microsoft Answers I know it is for the 64-bit but I didn't think there is a big deal!
Here are some problems:

1- Black screen with mouse only in boot startup (before the login screen and after the *Starting Windows* screen takes approximately 20 seconds

2- The *Other User* username didn't delete

3- Nothing in Extended tab in Services.msc BUT there are in Standard tab

I ran Startup Repair and used restore point but didn't help!

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Problems before deleting the key:

Very slow computer, so I used registry cleaners! It WORKED but I think it deleted Important Windows registry, so some programs won't work probably and clicking buttons on these programs won't work!
I use too much Registry Cleaners!
The black screen was before deleting the key! But after deleting the key it become slower!

Very slow windows startup! so I stopped services and startup programs!

After Installing an app! Services won't load automatically
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I think I need a Registry Repair tool! If there, please tell me where I can find?

I didn't upgrade to Windows 7 Service Pack 1 yet!

Thanks!
addas

So-called registry cleaners can do more harm than good so you're best bet is a system restore to a point before you deleted this registry key.

You can then investigate why your computer has slowed down.

Check out this tutorial, which explains how to optimize your Windows installation and so improve performance.

Optimize Windows 7

If ever you do decide to edit the system registry again, ALWAYS back it up first.

Thanks seavixen32 for reply!
My computer is totally optimized, I use a Tune Up application that made all those optimizations!
I only want to fix the problems listed above! and the most important problem I need to solve that I want to have a the Default Registry key! Please tell me where can I find it, and my registry cleaners deleted the backups!
Thanks,
addas

Well, your so-called tune-up application has most likely screwed your system.

In the absence of any restore points I'd be inclined to carry out a repair install providing you have a Windows DVD.

Repair Install

Make sure you backup any important data first.

The "Other User" entry is most likely the option to log in as any user but the one that was most recently logged in. I highly doubt it's removable.

That aside, nuking keys and values within the registry without any form of safety net or knowledge on what the effects are is a very hazardous undertaking.
Your best bet now is a repair install using your windows 7 DVD or repair partition (the latter applying with some OEM vendors such as HP, Dell, et al) or - if your problems continue - complete format and reinstall from scratch. Either way, do a complete backup of your userdata before going down either route just in case it all turns pear-shaped.

For what it's worth, purported "PC optimisation" software isn't worth the effort - shouldn't be too surprising if the cause of your problems is due to the same software that claims to improve your machine.