Performance effect of adding a new index

Hi there,
I have a table with about 10-20 insert per minutes and it can carry up to 500,000 records, except the primary key this table doesn't have any index, I need to make some reports based on a field that's System Date, this report shows in a web interface and run a few times per day, I heard that adding index on table with lot's of insert downgrade the insert performance,
How much do you think adding this index effect the general performance of this database? What can I do to minimize the performance effect?

Server Configuration:
Oracle 10g
Windows 2003
No Raid

Thank you in advance - Sam Received on Tue Apr 10 2007 - 21:37:51 CDT