can't read file

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i used CRM in my SBS2003 with sp1. i tried to edit an xml file using another
program for redeployment purpose of CRM. but it produce an error check that
file is readonly. i didnt feel it the problem of crm because i did it another
machine easily. i feel it is some problem of security . i gave full allow
security option for that file. is there any security option for cahnging
files with other programs.
replies will appreciated.
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