Yes, the location of sitedata can be changed. 

To change the location, complete the following steps:

NOTE:  These steps assume the default path for sitedata is c:\program files\ensim\sitedata

1. Copy all the data from c:\program files\ensim\sitedata to the destination path (for example, d:\sitedata).  
2. Stop the following services: 
   1. IIS Admin Service (This will stop WWW, FTP and SMTP) 
   2. Virtualhosting
   3. MailMax SE - ImapMax IMAP4
   4. MailMax SE - MailMax SMTP
   5. MailMax SE - PopMax POP3
   6. MailMax SE – QueMax
3. Rename the folder c:\program files\ensim\sitedata to sitedata.old.  
4. Create a link from c:\program files\ensim\sitedata to d:\sitedata.  This can be done with the linkd utility as follows: 
   1. Go to the command prompt. 
   2. Change your drive to C drive.
   3. cd \progra~1\ensim
   4. linkd sitedata d:\sitedata
   5. This will create a link between c:\program files\ensim\sitedata and d:\sitedata.
5. Now all the sitedata will be stored in d:\sitedata.