DELL GX60 WITH WINDOWS XP. MACHINE RE-STARTS AT ANY MOMENT

If you look at the top of the round shaped electrolytic capacitors, the good ones are flat, the bad ones are domed (internal pressure deforms the top of the capacitor and can explode).
Make sure you replace with the same capacitance and working voltage or slightly higher voltage.
These capacitors are polarized, make sure you don't solder them the wrong way.
Also the RAM may not make proper electrical connection, it can cause re-booting problems, remove the RAM and insert them a couple of times.
Over heating problems can also shut a computer down, make sure the fans are working properly, vacuum/remove dust from the fans (ie CPU fan & heatsink also from power supply and vents)

The ones that failed most in DELL's had a mark looking like a "+" or an "X" depending on your point of view. The ones that had "K"'s on top were usually the good ones.