PSU 750W Problems.... DOA?

[Zzonkers]

Building a new pc not all the parts are here yet but I'm deciding to test what I can for DOA so i know I'm good to go when everything is here. . I plugged it into my 2008 Dell studio 540 and its doesnt boot.... The case light should be white but its orange like its in standby and it turns my single case fan on for about 5 seconds then it stops spinning but my cup fan keeps spinning. Though they don't spin fast for a few seconds at start up then slow down like they normally do they just start spinning slowly. I have tried reseating the connections reseating ram and unplugging my gpu. Nothing works so is it that my computer being an old dell is not compatible which I dont even think thats possible or should I return it to newegg and hope I get a replacement before christmas.

 

[Zzonkers]

Also this CAPTONE is a 20+4 pin can you use those with 24pin mobos? thats what my dells is and the msi gaming 5 i just got is