Disk performance is dependent on many factors, including environment (operating system), workload on computer, memory available, cache size, fragmentation of disk, etc.
Check for latest updates to
1. Windows Server 2008
2. Disk driver file.
Check for disk fragmentation
Use utilities to check if bottleneck on memory (RAM) or disk I/O. Add more RAM if necessary.
Read Windows Server 2008 user guide and follow trouble-shoot instructions.
