How to convert exist Block Blob to PageBlob
No. Once a blob is created/uploaded you can't change the blob type. Unfortunately you would need to recreate/re-upload the blob. However I'm somewhat surprised. You mentioned that you copied the blob from one storage account to another. Copy Blob operation within Windows Azure (i.e. from one storage account to another) preserves the source blob type. It may seem a bug in CloudBerry explorer. I wrote a blog post some days ago about moving virtual machines from one subscription to another (http://gauravmantri.com/2012/07/04/how-to-move-windows-azure-virtual-machines-from-one-subscription-to-another/) and it has some sample code and other useful information for copying blobs across storage account. You may want to take a look at that. HTH.