I came to know many upgrade issues questions, here are little bit detail for you while upgrading.
Keep following things in your mind if you are upgrading from MS CRM 3.0 to CRM 4.0
- Any Un supported customization will not upgrade
- Any 3rd party tool will not upgrade like C360 components etc. It will give you trouble so first remove that and check your vendor for upgradeable version for CRM 4.0, I am sure they are upgrading it.
- Any Connector like GP Connector, Biztalk Adapter will not upgrade
- CRM Mobile Express 3.0 will not upgrade
- CRM Accelerator for Seible will not supported to upgrade.
- Sharepoint list webpart will not upgrade
- Datamigration Pack will not upgrade
- Your custom calls or code will not upgrade, you have to rebuild your code using new crm services, atleast you have to use crm discovery as it is multi-organizational system.
- CRM Outlook Client will not upgrade
- Any custom code for outlook will not upgrade
- CRM Callouts need to modify and register with Plugin Register tool
- Your code web to lead or web to contact need to modify by using CRM Discovery Service and updation manually
- Any Code will not upgrade by MS CRM 4.0, you have to do manually all configuration
- Assembly written for workflow will not upgrade and link, you have to again link with it
Standard CRM Reports will be upgraded and link will automatically build with new CRM SRS connection. but following types of reports will not upgrade
- The Reports has been modified to use expressions for linking will not upgrade.
- The Report has been modified to use stored procedures will not upgrade.
- Reports that use information about workflow, such as sales pipeline report etc will not upgrade.
Dear Consultants / implementers please check above list, you have to care while upgrading as there are 90% questions so far about this on forums.
Hopefull it will help you alot to understand CRM Upgrade issues.