Tide will also work if you don't have a UV pen. I don't recommend it inside of a computer, but it looks great on the walls of a dorm room!

(On a related note, did you know that beer when ingested then regurgitated glows purple?

I wouldn't put that inside of a computer either, but looked awesome!

)
I have a UV light and a blue light and can barely see the glow from the UV reactive stuff in my case. (All the wires are sleeved with UV reactive sheaths, plus the IDE and floppy cables are UV reactive.) I might just get a red tube to replace the UV, or try it without the blue and check it out.