I just need to know which of these would be faster (Photoshop, gaming, video editing)

Old:
Intel Pentium 4 570 3.8GHz 800MHz 1MB Socket

New:
Intel Pentium D 945 Presler 3.4GHz 2 x 2MB L2 Cache LGA

Thank you!

According to tomshardware.com cpu compairison chart, the slower processor is actually faster. Now, all they had was the Intell P4 940, and not the 945 that you listed. I can't imagine that there's a huge difference between the two (940 & 945, although I didn't see the 940 listed on newegg.com!), but there's a substantial difference in speed between the 2 you listed, with the P4 D 945 being faster. Reason it's faster is that it's dual core, so ensure that your mobo will support dual core!

Didn't know this chart, thank you very much for the help!

No problem! Glad to help. Just remember that the dual core is faster than the single core despite it's slower speed rating!