Helpdesk application

Hi All,

We are looking to replace our current helpdesk solution(Microsoft CRM)with an ITIL compliant helpdesk solution that has the following requirements:

Web based
Easy for end users and technicians to use
Fully configurable fields so the end user is not confused
Solid reporting engine for SLAs met.
Can be easily customised
Reasonable cost
Windows based
Good support background
The usual helpdesk features i.e. departmental categories, active directory integration etc

Can you let me know what solutions you currently have in place, how you find it (good or bad), what you would recommend, what I really should be looking for in such a product etc

Any assistance would be appreciated.

Regards