removing and reinstalling .NET Framework (long post)

Using WinXP. Because of what appears to be .NET Framework corruption, I've
been trying to remove all versions of .NET Framework from my Dell laptop
prior to reinstalling. I contacted Microsoft Support after encountering
problems removing it. At this point, my case has been escalated a level
there, but I'm worried about the latest instructions.

Background: To remove all versions, I used the .NET Framework cleanup tool.
However, it removed only versions 2.0 SP2 and 3.0 SP2. Versions 1.1 and 3.5
SP1 are still on my computer. Moreover, after I used the removal tool, I
began getting an error message on startup:
SecureUpgrade.exe - Application error
The application failed to initialize properly (0xc0000135). Click on OK to
terminate the application.

When I explained all this to the Microsoft tech person by email, she
suggested the following, and I thought I'd ask here before doing anything
more. The instructions are as follows. My question: Can I make things worse
by following them?

1. Create and run a batch file containing the following commands:
echo off
Rd C:\Windows\assembly /s /q
Rd "C:\Windows\Microsoft .NET" /s /q
Del C:\Windows\System32\mscoree.dll /q
Del C:\Windows\System32\URTTemp\mscoree.dll /q
del %temp% /Q /F
MSIexec /unregister
MSIexec /regserver
Reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramewo rk" /f
Reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microso ft Integration" /f
Reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework SDK" /f
Reg delete "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup" /f

2. Run CCleaner, as follows:
*In Internet Explorer list, check "Temporary Internet Files", "History",
"Last Download Location",
*In Windows Explorer list, check "Other Explore MRUs"
*In System list, check "Empty Recycle Bin", "Temporary files", "Memory
Dumps", "Chkdsk File Fragments"
*Click Analyze and then Run Cleaner.
*In Registry panel, click Scan for issues and then click Fix selected
issues.

3. Download the .NET Framework 3.5 SP1 Full Package.

4. Install the update in clean boot mode. Disable all startup items and
third party services when booting by doing the following:
*Click "Start", go to "Run", and type "msconfig" (without the quotation
marks) in the open box to start the System Configuration Utility.
*Click the "Services" tab, check the "Hide All Microsoft Services" box and
click "Disable All" (if it is not gray).
*Click the "Startup" tab, click "Disable All" and click "OK".
*Click "OK" to restart your computer to Selective Startup environment.
*When the "System Configuration Utility" window appears, please check the
"Don't show this message or launch the System Configuration Utility when
Windows starts" box and click OK.

If I run into more problems, I'm to email Microsoft screenshots of any error
messages.

Does this look like a reasonable approach to the current problem?

Thank you very much for your help!

Jo-Anne