[FirElem3n7]

Hello,
i am using windows xp pro with SP1. i recently installed on my system Microsoft Platform SDK and vc++. at the start both of them worked great! but once i tried reinstalling both of them i got some Errors:

1.first of all when i try uninstalling the components: "common setup files" and "Registered environment variables" from microsoft platform sdk i get the following error:
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100663296: 1: 0 2: PSDK-x86.msi 3: {7FC0D670-057F-4D50-A7B8-2CA291360708} 4: {7FC0D670-057F-4D50-A7B8-2CA291360708}; 5: 0 6: 1 7:1 16777216 : ERROR 1706. No valid source could be found for product common setup files (3790.0). The windows installer cannot continue. 1603 : A Windows instaler error has occurred. 512 : Installation faild with one or more errors. Please correct the errors and/or try again.
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2. my second problem is when i try starting VC++. when i start it i get this error:
Title: MSDEV.exe - Unable To Locate Component
Message: This application has failed to start because devshl.dll was not found. Re-installing the application my fix this problem.
i tried Re-installing the applicaion but it failed every time with the same error.
What can i do to solve those problems?
Thanks Ahead.