I have a Celsius R610 with a blinking red light on front of tower. What does it indicate?

It should fit, the R610 is SSI EEB v3.0 footprint (12" x 13"), while the Micro X6DVL-EG2 is 12" length x 10" width, so you should have no problem fitting the motherboard in that case.

That system has support for windows XP and Linux (RedHat and SuSE) so if you want to install windows server 2008 you will need windows 2008 compatible drivers, maybe this link bellow can help you to identify right drivers (It is detailed technical motherboard manual for that system)
Manual

First, is it clean, open case and check for dust. Clean fans , CPU , etc., if necessary. Open Task Manager , What is you Preformance, CPU % Memory %? What is running in Processes? Here is a little free program to adjust fans: http://www.filehippo.com/download_speccy/ The orange light is it the HDD led? You can use CCLEANER free: http://www.filehippo.com/download_ccleaner/. You can clean the junk from your system and in TOOLS, STARTUP, Disable ALL unnessary programs from startup, that will speed up your system.

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Reseat the memory sticks. Make sure the sticks all match if any have been changed. You can not mix types of sticks. Clear all logs in bios.

You should be able to purchase these mounts from your friendly computer shop or computer repair shop.

You may need to enable it in bios, maybe with the new os you need to update the chipset drivers or bios!

It Indicate that your PC is processing request by using CPU

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set one the master and the other slave to the master .that should work.