You'll need to fine-tune the permissions/trust level granted to the ASP.NET account.
See these articles for hints :
http://www.codeproject.com/KB/aspnet/ASPNETService.aspx
http://msdn.microsoft.com/en-us/magazine/cc163821.aspx
Also, download the source code for Abidar and play with it :
http://www.codeplex.com/abidar
Abidar is an ASP.NET task scheduler library written with C# for .NET 2.0 and 3.5.
Juan T. Llibre, asp.net MVP
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http://asp.net.do/foros/
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