Few days ago, I wanted to rebuilt 2 old Dell PowerEdge 1950 servers when I found out that DVD drives were dead on both of them. Luckily, I had a USB memory stick handy, which I made into bootable Windows Server 2008 R2 installation media.
To create it, you need USB memory stick with at least 4GB of capacity and original Windows Server installation DVD.
1. Plug-in your USB drive
2. Launch Command Prompt as Administrator
3. In Command Prompt launch diskpart utility by typing “diskpart” (without quotes) and hitting enter.
4. In diskpart, type “list disk” to see all currently mounted drives. Note the number of the USB drive.
5. Execute following commands replacing 1 with your disk number if different.
select disk 1 clean create partition primary select partition 1 active format fs=ntfs quick assign exit
6. You drive is now ready, just copy ALL contents from the original installation media to the USB drive.
7. Boot from USB!

