After his father's death, Andrew's mother Elizabeth remarried to Sir Robert Lytton, who became Keeper of the Wardrobe to Henry VII in 1492. Lytton acquired the reversion of the manor of
Knebworth in Hertfordshire from the estate of Sir Thomas Bourchier (died 1491, a younger son of the
1st Earl of Essex), who had it in right of his former wife Isabel (Barre), widow of
Humphrey Stafford, 1st Earl of Devon. Bourgchier had married secondly Anne Andrews (widow of Sir John Sulyard and sister of Elizabeth), who long survived him and died at
Wetherden, Suffolk in 1520. Andrew married Elizabeth Blount, sister and coheir of
Edward Blount, 2nd Baron Mountjoy. His brother John Wyndsore, of the
Middle Temple, married Anne Fiennes, daughter of Sir Thomas Fiennes of Claverham in
Arlington, East Sussex: his brother Anthony Wyndsore married Elizabeth daughter of Henry Lovell and Constance Hussey, heiress of
Harting, Sussex. His sisters Elizabeth and Alice married Richard Fowler and George Puttenham respectively. Among Andrew's inheritances were estates in Suffolk including Andrews Hall in
Sproughton and
Stoke, property coming from the Andrewes side, mentioned in the 1522 Perambulation of
Ipswich and in Andrew's will. Throughout his life Wyndsore acquired estates in many parts of the kingdom. Having entered the Middle Temple, during the 1500s he was appointed J.P. of several counties (including Hampshire (1502), Middlesex (1505) and Buckinghamshire (1507)), was Commissioner for Subsidies for Middlesex and Buckinghamshire in 1503, was Steward to the lands of
Edward Stafford, 3rd Duke of Buckingham in Hampshire in 1504, and held various other commissions in those counties and in London and Essex. He was a
feoffee for Henry VII in a 1504 land transaction concerning
Syon Abbey, where his sister Margaret led a religious life. He also acted as feoffee for his brother-in-law
Edmund Dudley,
Speaker of the House of Commons, who had married his sister Anne. making Dame Elizabeth his executor and Andrew Wyndsore and Edmund Dudley his supervisors, Andrew was appointed Keeper of the Wardrobe in his place, opening great opportunities for enrichment. In handling the King's finances Dudley amassed wealth and estates, and became a foremost mediator of royal favour and influence. Edmund Dudley and
Richard Empson were immediately imprisoned on the death of the King in 1509, but Wyndsore was among those to be invested
Knight of the Bath at the Coronation of King
Henry VIII. During their indictment and conviction for
Constructive treason Dudley and Empson were held in the
Tower of London, where Dudley declared a will making
Bishop FitzJames, Sir Andrew Wyndsore,
Dean Colet and
Dr Yonge his executors or feoffees. Wyndsore was thereby joined in Dudley's attempt to resist the predatory intentions towards his estates of
John Ernley, who as
Attorney General for England and Wales was deeply embedded in the new king's favour. Following Dudley's execution in 1510, in which year Wyndsore sat as Member of Parliament for
Cricklade, these matters came into court in 1512. ==Knight service==