XP Pro and Outlook 2003 fully up-to-date.
About a year and a half ago I installed Outlook 2003 to use the calendar portion (locally) only.No Exchange, no email config installed. Whenever I open the calendar, it takes over associations for system default email client, along with mailto:, vcf and msg. Fortunately the two mail clients that I use warn me that Outlook has attempted to hijack, but it is really annoying to click thru the warnings to keep the settings I want. Occasionally, a monthly Windows/Office update will fix the problem...until the next patch cycle. The option in Outlook to make it the default mail client isn't checked, although in desperation I've tried toggling it a few times. Have considered upgrading to Outlook 2007, but am afraid that will screw up Word/Excel 2003 which I need for compatibility at work. And i suspect it is impossible to have several versions of Office on one box.
Any suggestion? Please!

Bob