Hardware and performance

My Moodle server  configured with following details  :

OS  Windows 8 Ent. With SP2 

Application S/w                        Version

1. Moodle                                2.5                         
2. Wampserver                      2.1
3. MySQL                                  5.5.8
4. PHP                                        5.3.5
5. Apache                                 2.2.17

Client end using Safe Exam Browser

1. SEB                                         1.8.2

Last few years,  we are using moodle 2.0 with all other same version support application software( WAmserver,php,apache,seb , mysql) .

It was running smoothly at a time more than 250 system ( client ) at a time. But after updating moodle version 2.5  facing problem like

1. Server Task Manager Show httpd.exe or SQL service CPU utilization 100%
2. More than 60 Client (user’s not allowed at a time ) system got hanged and stuck.
3. On SEB client end , error window flash “document does not contain data”

I already done yours performance updating check, but no effect same as above mention.

Kindly  revert with prompt solution as earliest as possible, so cannot stuck up in future.