I was given a Lenovo desktop PC recently that wouldn't boot. Upon opening, I immediately spotted a couple of cracked/swollen caps.
These capacitors were 1,000uF 6.3V caps. My experience is the voltage does not really matter that much, as long as the rating is equal to or greater than the original. So, rummaging through my circuit boards, I found a couple 1,000uF caps, both which much higher voltage ratings. Because of their different sizes (form factor), I added leads and soldered those in
The soldering job was a challenge - the multi-layer board consumed a lot of heat, so getting the solder to melt enough to both desolder the old parts, and solder in the new ones was difficult. But the board turned out to be significantly tough.
It booted up and ran all night without any issues!