Noobie Question - What are the sizes of ATX I can fit in my case?

Solution
Your desktop is described on HP support page as mid-size ATX but n other website it is described as a Mini-Tower (would not fit full ATX motherboard)
On the other hand from pictures of your desktop maintenance manual it doesn't seem to be able to fit a full ATX motherboard (there is no room for expansion vertically as the installed Micro-ATX motherboard seems to come very close to the power supply

you can go for a Micro ATX motherboards (same Form Factor as the one installed in your PC) or the smaller Mini ITX) which latest iterations come packed with most full ATX motherboards features..

HP Pavilion P6210F Mini Tower System >>...

R0GG

Distinguished
Your desktop is described on HP support page as mid-size ATX but n other website it is described as a Mini-Tower (would not fit full ATX motherboard)
On the other hand from pictures of your desktop maintenance manual it doesn't seem to be able to fit a full ATX motherboard (there is no room for expansion vertically as the installed Micro-ATX motherboard seems to come very close to the power supply

you can go for a Micro ATX motherboards (same Form Factor as the one installed in your PC) or the smaller Mini ITX) which latest iterations come packed with most full ATX motherboards features..

HP Pavilion P6210F Mini Tower System >> http://www.stuartconnections.com/en/systems-with-cpu/345-HP-Pavilion-P6210F-Mini-Tower-System-Athlon-II-X4-26GHz-6GB-Ram.html
eJlCD6h.jpg

WZ5RuOu.jpg
 
Solution