There is no time limit on losses, regardless of whether they are business losses or CGT losses. You can hold them indefinitely until they are used up.
You cannot offset your internet losses against your CGT gains or losses. However, if you are CGT, you can try to offset them against your dividends income. But one must be careful here when 'connecting' or 'relating' the expense to dividends income because dividends income is usually quite passive in nature.
Computer you can deduct because the depreciation laws simply say you use it for earning assessable income. The 'assessable income' is neither defined as revenue or capital.
But again, you must apportion your computer use for income & private purposes.
