(1) There's an army of economists attached to the following places, who play happily amidst piles of the sort of data you seek. Only thing is, you really have to dig hard to find exactly what you want. Not so easy as simply Googling a search word.
Best of all, try to identify & contact individual economists personally & let them refer you to the right data. Give those fluffy bottomed Ph.D.'s some exercise!
United Nations Statistics Division
World Bank Development Data & Statistics
The African Development Bank
The Islamic Development Bank
Inter-American Development Bank
Asian Development Bank
(2)
Research librarian at any good university can aim your search at the right targets. Also, they know of lots of private and possibly fruitful-for-you databases you'll never hit with Google.
(3)
Economics Prof. at any good university can tell you where to find that data.
(4)
Computer trade associations probably can point you to marketing execs of member companies who have data like that, since "computer usage data" split out by country is fundamental
marketing data that any worthwhile Sales / Marketing Dept. will have, basic to their jobs. Only thing is, they may deem it proprietary and be unwilling to share it since you might be their competitor, but in that case, you could try asking them for summarized versions they would be comfortable releasing to you.
(5) Look into
US export trade data, for computers which would be a reasonable proxy indicator of PC consumption, implying usage. Only kink in that is, most PC exports probably are drop shipped from CHina / Taiwan directly to the customer nations, not reflected in US export data. Still you might look into what you can plow up to serve as a proxy indicator. You could even explore US export trade data for software, as a more indirect, yet maybe still suggestive, indicator of computer usage in LDCs.