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「社外持ち出し禁止PC」というデカいシールが貼られたPCで…
→ “On a PC with a huge sticker that says 'No Taking Outside the Office'...”
社外 shagai = outside the company (noun)
社 sha = company / society
外 gai = outside / exterior
持ち出し mochidashi = taking out / removal (noun)
持 mo = to hold / carry
ち chi = small/telescopic form of 'motsu'
出 dashi = to come out / exit
禁止 kinshi = prohibition / ban (noun)
禁 kin = forbid / prohibit
止 shi = stop / cease
PC PC = personal computer (noun)
と to = that (quote particle)
いう iu = saying / called (verb)
デカい dekai = huge / big (adjective)
デカ deka = big (loanword from English)
い i = adjective ending
シール shīr¹u = sticker (noun)
が ga = subject marker particle
貼られた harerareta = was pasted / was stuck (passive verb)
貼 ha = to paste / stick
ら ra = causative/passive auxiliary
れ re = passive auxiliary
た ta = past tense marker
PC PC = personal computer (noun)
で de = at / on / using (location/instrumental particle)
… = ellipsis (indicating trailing off or suspense)