Yes, it is boot from Lan.. but your Lan card has to be able to handle it and usually you can find it in your BIOS, as far as the installation.. i'll be back with that
My Computer
Computer Manufacturer/Model Number
HP Pavilion Elite HPE-410f
OS
Windows 7 Ultimate x64
CPU
AMD Phenom x6 1045t
Motherboard
N/A
Memory
8 GB
Graphics Card(s)
ATI Radeon HD 5570
Sound Card
Realtek Highdefinition Audio / 5.1 Dolby Setup
Monitor(s) Displays
HP w2207h Widescreen
Screen Resolution
1680*1050
Hard Drives
1 TB (fixed), 320 Portable maxtor, Server Hard drives
You can access another network computer to run the extracted installer files from your current OS, to install to another partition and sometimes to overwrite the current partition.
Another method to go diskless is to copy the installer's extracted files to a 3gb Primary partition you create by shrinking your current OS, then run the Setup File from there. This should allow you to overwrite the current OS partition.
Best method is to boot a flash stick installer which has the ISO written to it by Win2Flash or UltraISO. This allows you to use the Custom>Drive options to delete, repartition and format the HD - which can only be done from booting the installer.